Engine controlling system which reduces the engine output upon detection of an abnormal condition

ABSTRACT

An engine controlling system for a vehicle suitable for use with an automobile. An output reduction control amount setting means sets, when an abnormal condition detection signal of a throttle valve controlling means or a throttle valve control amount setting means is developed and a range detection signal indicates a neutral range, a control amount of an engine output reducing means such that the reduction of the output power of an engine may increase as the engine speed represented by an engine speed detection signal increases. On the other hand, when such abnormal condition detection signal is developed and the range detection signal indicates a running range, the output reduction control amount setting means sets a control amount of the engine output reducing means such that the reduction of the output power of the engine may be decreased as the accelerator pedal operation amount represented by an operation amount detection signal increases. With the system, even an abnormal condition takes place in a throttle valve controlling system, the engine can be adjusted within a predetermined range.

This application is a continuation of United State application Ser. No.07/469,406 filed Jul. 27, 1990 now abandoned.

FIELD OF THE INVENTION

This invention relates to an engine controlling system for a vehiclewhich is suitable for use with an automobile.

BACKGROUND OF THE INVENTION

Conventionally, various systems for automatically controlling therunning speed of a vehicle have been provided. Such control may be acontrol for causing a vehicle to run at a constant speed in accordancewith an aimed speed, another control for causing a vehicle to run in anaccelerated condition in accordance with an aimed acceleration or thelike. In such controls, it may be recommended to actuate a throttlevalve of an engine to adjust the output power of the engine so that thevehicle may run at an aimed speed or at an aimed acceleration.

By the way, it is advantageous in respect of control to perform suchactuation of a throttle valve in automatic running control of a vehicleby means of an electrically driven throttle actuator.

Such throttle actuator, however, may possibly fail such that it stops ata certain opening because of, for example, disconnection thereof. Evenin the case of such failure, it is desirable that the output power ofthe engine can be adjusted within an allowable range by somedisposition.

The present invention has been made in view of such a subject asdescribed above, and it is an object of the present invention to providean engine controlling system for a vehicle which can adjust the outputpower of an engine within a fixed range even when a throttle actuatorfails.

DISCLOSURE OF THE INVENTION

In order to attain the object, according to the present invention, thereis provided an engine controlling system for a vehicle, which comprisesan accelerator pedal of the vehicle, an operation amount detecting meansfor detecting an operation amount of the accelerator pedal anddeveloping a corresponding operation amount detection signal, a throttlevalve for changing the amount of air to be taken into an engine of thevehicle to adjust the output power of the engine, a throttle valvecontrol amount setting means for setting a control amount of thethrottle valve in response to the operation amount detection signal, athrottle valve controlling means for controlling the throttle valve toopen or close in response to the control amount, an abnormal conditiondetecting means for detecting an abnormal condition of the throttlevalve controlling means or the throttle valve control amount settingmeans and developing a corresponding abnormal condition detectionsignal, a speed change gear means provided in the vehicle and having aplurality gear positions, an automatic speed change gear controllingmeans for controlling changing over between the gear positions of thespeed change gear means, a range changing over means for selectivelysetting the range of the speed change gear means at least to a runningrange or a neutral range, a range detecting means for detecting a rangeset by the range changing over means and developing a correspondingrange detection signal, an engine speed detecting means for detecting arotational speed of the engine and developing a corresponding enginespeed detection signal, an engine output reducing means for reducing theoutput power of the engine, and an output reduction control amountsetting means for setting, when the abnormal condition detection signalis received and the range detection signal indicates the neutral range,a control amount of the engine output reducing means such that thereduction of the output power of the engine may be increased as theengine speed represented by the engine speed detection signal increases,but setting, when the abnormal condition detection signal is receivedand the range detection signal indicates the running range, a controlamount of the engine output reducing means such that the reduction ofthe output power of the engine may be decreased as the accelerator pedaloperation amount represented by the operation amount detection signalincreases. It is to be noted that the neutral range here includes aparking range.

With the engine controlling system for a vehicle according to thepresent invention described above, when the abnormal condition detectingmeans detects an abnormal condition of the throttle valve controllingmeans or the throttle valve control amount setting means and outputs anabnormal condition detection signal and the range detection signalindicates the neutral range, the output reduction control amount settingmeans sets a control amount of the engine output reducing means suchthat the reduction of the output power of the engine may be increased asthe engine speed represented by the engine speed detection signal fromthe engine speed detecting means increases. On the other hand, when theabnormal condition detecting means outputs the abnormal conditiondetection signal and the range detection signal indicates the runningrange, the output reduction control amount setting means sets a controlamount of the engine output reducing means such that the reduction ofthe output power of the engine may be decreased as the accelerator pedaloperation amount represented by the operation amount detection signal.The engine output reducing means reduces the output power of the enginein accordance with the control amount set in this manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(i) to 1(iii) are block diagrams schematically showingconstruction of principal components of an engine controlling system fora vehicle to which the present invention is applied;

FIG. 2 is a block diagram schematically showing general construction ofthe vehicle engine controlling system;

FIG. 3 is a block diagram schematically showing general construction ofa treadled amount detecting section of the vehicle engine controllingsystem of FIG. 2;

FIG. 4 is a block diagram schematically showing general construction ofa throttle valve pivoting section of the vehicle engine controllingsystem of FIG. 2;

FIG. 5 is a block diagram schematically showing general construction ofa speed/acceleration detecting section of the vehicle engine controllingsystem of FIG. 2;

FIG. 6 is a front elevational view of an automatic cruise switch of thevehicle engine controlling system of FIG. 2;

FIG. 7 is a circuit diagram showing an electric circuit which connectsthe automatic cruise switch of FIG. 6 to a control section of thevehicle engine controlling system of FIG. 2;

FIG. 8(i) is a flow chart of a main routine illustrating generaloperation of the vehicle engine controlling system of FIG. 2, FIGS.8(ii) to 8(iv) are flow charts of interrupt routines illustratingoperation of the vehicle engine controlling system of FIG. 2, FIG. 8(v)is a flow chart showing contents of fail safe control for compensatingfor an error in actual acceleration calculated by third interruptcontrol illustrated in FIG. 8(iv), FIG. 8(vi) is a flow chart showingcontents of another fail safe control (second fail safe control) forcompensating for an error in actual acceleration calculated by the thirdinterrupt control illustrated in FIG. 8(iv), and FIG. 8(vii) is a flowchart showing a procedure of setting car weight data;

FIG. 9 is a flow chart illustrating details of operation of directthrottle movement control at step A117 of the main routine of FIG. 8(i);

FIG. 10 is a flow chart illustrating details of operation in non-directthrottle movement control at step A116 of the main routine of FIG. 8(i);

FIG. 11 is a flow chart illustrating details of operation ofacceleration mode control at step C137 of the flow of FIG. 10;

FIG. 12 is a flow chart illustrating details of operation of automaticcruise mode control at step C144 of the flow of FIG. 10;

FIG. 13 is a flow chart illustrating details of operation of changingover switch control at step E128 of the flow of FIG. 12;

FIG. 14 is a flow chart illustrating details of operation ofacceleration switch control at step E121 of the flow of FIG. 12;

FIG. 15 is a flow chart illustrating details of operation ofdeceleration control at step E131 of the flow of FIG. 12;

FIG. 16 is a flow chart illustrating details of operation of aimed speedcontrol at step E133 of the flow of FIG. 12;

FIG. 17 is a flow chart illustrating details of operation ofacceleration control at step E122 of the flow of FIG. 12;

FIG. 18 is a flow chart illustrating details of operation of control ofdetermination of an aimed acceleration DVS₄ at step J115 of the flow ofFIG. 16;

FIGS. 19 to 26 are graphs illustrating relationships between parametersof a map used for control by the engine controlling system and variablesread out in accordance with such parameters;

FIGS. 27(i) and 27(ii) are graphs showing exemplary changes of an aimedacceleration and a running speed with respect to a time elapsed after anacceleration switch of the vehicle engine controlling system shown inFIG. 2 is changed over to change the designation by a running conditiondesignating section of the control section to an accelerated running;

FIGS. 28(i) and 28(ii) are flow charts illustrating details mainly ofcontrol upon riding on an upward slope of contents of control of anautomatic transmission by an automatic transmission controlling device,FIG. 28(iii) is a flow chart illustrating contents mainly of controlupon riding on a downward slope of the contents of the control of theautomatic transmission by the automatic transmission controlling device,and FIGS. 28(iv) and 28(v) are flow charts illustrating contents ofcontrol as modifications to the control upon riding on a downward slopeshown in FIG. 28(iii);

FIG. 29(i) is a flow chart illustrating contents of control of a maincontrol upon quick braking among contents of control of the automatictransmission by the automatic transmission controlling device, FIG.29(ii) is a flow chart illustrating contents of control of an interruptcontrol executed in a 20 ms timer interrupt to the main control, andFIG. 29(iii) is a map which is used in the 20 ms timer interrupt controlto find out time data therefrom;

FIG. 30 is a map for the setting of a control parameter with which theautomatic transmission is to be controlled to perform normal speedcontrol in an automatic cruise mode control;

FIGS. 31(i) to 31(iv) are flow charts illustrating contents of controlin speed change shock reducing control;

FIGS. 32(i) to 32(iii) and 33(i) to 33(iii) are time charts illustratingsuch speed change shock reducing control;

FIGS. 34(i), 34(ii), 35, and 36 are maps for use in the speed changeshock reducing control;

FIGS. 37(i) and 37(ii) are flow charts illustrating contents of controlof a throttle actuator fail control for allowing torque adjustment to beexecuted within an allowable range when the throttle actuator fails; and

FIGS. 38 and 39 are maps for use in the throttle actuator fail control.

BEST FORM IN EMBODYING THE INVENTION

In the following, a preferred embodiment of the present invention willbe described with reference to the drawings. FIGS. 1(i) to 39 show anengine controlling system for a vehicle as a preferred embodiment of thepresent invention. Of FIGS. 1(i) to 39, FIGS. 1(i) to 7 showconstruction of the system of the embodiment, and particularly FIGS.1(i) to 1(iii) are block diagrams conceptually showing principalportions of the system of the present invention while FIG. 2 is a moredetailed block diagram of the entire engine controlling system for avehicle of the present invention.

Construction of principal portions of the present system will first bedescribed with reference to FIGS. 1(i) to 1(iii). Referring first toFIG. 1(i), the engine controlling system for a vehicle is generallydenoted at 1. The vehicle engine controlling system 1 includes anaccelerator pedal 27, and an operation amount detecting means 102 fordetecting an operation amount of the accelerator pedal 27. The operationamount detecting means 102 corresponds to a treadled amount detectingsection 14 shown in FIG. 2. The vehicle engine controlling system 1further includes a throttle valve 31.

The vehicle engine controlling system 1 further includes a throttlevalve control amount setting means 103 for setting a control amount ofthe throttle valve 31 in response to an operation amount detectionsignal from the operation amount detecting means 2. Referring now toFIG. 1(iii), the throttle valve control amount setting means 103includes, for example, an accelerator pedal operation conditiondetecting section 121 for detecting a treadled condition of theaccelerator pedal 27 and cancellation of such treadled condition anddeveloping a corresponding detection signal, a first control amountsetting section 122 for setting, when a treadled condition detectionsignal is developed from the accelerator pedal operation conditiondetecting section 121, a control amount of the throttle valve 31 inresponse to an operation amount detection signal of the acceleratorpedal 27, a running condition selecting section 123 for selecting, whena treadled condition cancellation detection signal is developed from theaccelerator pedal operation condition detecting section 121, either oneof a constant speed running designating signal and an acceleratedrunning designating signal as an aimed running condition of the vehicle,an aimed speed setting section 125 for setting, when a constant speedrunning designating signal is developed from the running conditionselecting section 123, an aimed speed of the vehicle for the constantspeed running, a running speed detecting section 124 for detecting acurrent running speed of the vehicle and developing a correspondingrunning speed detection signal, a second control amount setting section126 for setting, when a constant speed running designating signal isdeveloped from the running condition selecting section 123, a controlamount of the throttle valve 31 with which the running speed of thevehicle represented by a running speed detection signal from the runningspeed detecting section 124 is to be made equal to an aimed speed fromthe aimed speed setting section 125, an accelerated running aimedacceleration setting section 127 for setting, when an acceleratedrunning designating signal is developed from the running conditionselecting section 123, an aimed acceleration for the accelerated runningof the vehicle, and a third control amount setting section 128 forsetting, when an accelerated running designating signal is developedfrom the running condition selecting section 123, a control amount ofthe throttle valve 31 in response to an aimed acceleration set by theaccelerated running aimed acceleration setting section 127.

Among those sections, the running condition designating section 123includes a manual selecting section 123a for selecting either one ofconstant speed running and accelerated running as an aimed runningcondition of the vehicle by manual operation thereof, a designatingsignal developing section 123b for developing, when constant speedrunning is selected by the manual selecting section 123a, a constantspeed running designating signal but developing, when acceleratedrunning is selected, an accelerated running designating signal, a finalaimed speed setting section 123c for setting, when an acceleratedrunning designating signal is developed from the designating signaldeveloping section 123b, a final aimed speed for the accelerated runningof the vehicle, and a running condition changing over section 123d forchanging over, when the absolute value of a deviation between a runningspeed of the vehicle represented by a running speed detection signalfrom the running speed detecting section 124 and a final aimed speed ofthe vehicle from the final aimed speed setting section 123c becomessmaller than a predetermined value, the output of the designating signaldeveloping section 123b from an accelerated running designating signalto a constant speed running designating signal.

The first control amount setting section 122 includes a treadledcondition aimed acceleration setting section 122a for setting, when atreadled condition detection signal of the accelerator pedal 27 isdeveloped from the accelerator pedal operation condition detectingsection 121, an aimed acceleration of the vehicle in response to anaccelerator pedal operation amount represented by an operation amountdetection signal from the accelerator pedal operation conditiondetecting section 121 and a changing rate of the accelerator pedaloperation amount, a treadled condition aimed output calculating section122b for calculating an aimed output power of the engine 13 in responseto an aimed acceleration set by the treadled condition aimedacceleration setting section 122a, and a treadled condition controlamount setting section 122c for calculating a control amount of thethrottle valve 31 in response to an aimed engine output power calculatedby the treadled condition aimed output calculating section 122b.

Meanwhile, the second control amount setting section 126 includes aconstant speed running aimed acceleration calculating section 126a forcalculating, when a constant speed running designating signal isdeveloped from the running condition selecting section 123, an aimedacceleration of the vehicle with which the running speed of the vehiclerepresented by a running speed detection signal from the running speeddetecting section 124 is to be made equal to an aimed speed of thevehicle from the aimed speed setting section 125, a constant speedrunning aimed output calculating section 126b for calculating an aimedoutput power of the engine 13 in response to an aimed accelerationcalculated by the constant speed running aimed acceleration calculatingsection 126a, and a constant speed running control amount calculatingsection 126c for calculating a control amount of the throttle valve 31in response to an aimed engine output power calculated by the constantspeed running output calculating section 126b.

Further, the third control amount setting means 128 includes anaccelerated running aimed output calculating section 128a forcalculating, when an accelerated running designating signal is developedfrom the running condition selecting section 123, an aimed output powerof the engine 13 in response to an aimed acceleration set by theaccelerated running aimed acceleration setting section 127, and anaccelerated running control amount setting section 128b for calculatinga control amount of the throttle valve 31 in response to an aimed engineoutput power calculated by the accelerated running aimed outputcalculating section 128a.

Referring back to FIG. 1 (i), the vehicle engine controlling system 1further includes a throttle valve controlling means 104 for controllingthe throttle valve 31 to open or close in response to a control amountset by the throttle valve control amount setting means 3. The throttlevalve controlling means 104 corresponds to a throttle valve pivotingsection 26 shown in FIG. 2.

The vehicle engine controlling system 1 further includes an abnormalcondition detecting section 105 for detecting an abnormal condition ofthe throttle valve controlling means 104 or the throttle valve controlamount setting means 103 and developing a corresponding abnormalcondition detection signal. Referring to FIG. 1 (ii), the abnormalcondition detecting means 105 includes a control amount detectingsection 105a for detecting an actual control amount of the throttlevalve 31 and developing a corresponding control amount detection signal,and an abnormal condition detection signal developing section 105b fordeveloping an abnormal condition detection signal when the differencebetween an actual control amount of the throttle valve 31 represented bya control amount detection signal from the control amount detectingsection 105a and a control amount set by the throttle valve controlamount setting means 103 comes out of a predetermined range.

Referring back to FIG. 1 (i), the vehicle engine controlling system 1further includes a speed change gear means 106 provided in the vehicleand having a plurality of gear positions, and an automatic speed changegear controlling means 107 for controlling changing over between thegear positions of the speed change gear means 106. In FIG. 2, anautomatic transmission 32 corresponds to the speed change gear means 106and automatic speed change gear controlling means 107. The vehicleengine controlling system 1 further includes a range changing over means108 for selectively setting the range of the speed change gear means 106at least to a running range or a neutral range. A shift selector 29 inFIG. 2 corresponds to the range changing over means 108. A rangedetecting means 109 is provided for detecting a range set by the rangechanging over means 108 and developing a corresponding range detectionsignal, and a shift selector switch 17 in FIG. 2 corresponds to therange detecting means 109.

The vehicle engine controlling system 1 further includes an engine speeddetecting means 110 for detecting a rotational speed of the engine 13and developing a corresponding engine speed detection signal, and anengine speed detecting section 21 in FIG. 2 corresponds to the enginespeed detecting means 110. The vehicle engine controlling system 1further includes an engine output reducing means 111 for reducing theoutput power of the engine 13, and an output reduction control amountsetting means 112. The output reduction control amount setting means 112sets, when an abnormal condition detection signal is developed from theabnormal condition detecting means 105 and the range detection signalfrom the range detecting means 109 indicates the neutral range, acontrol amount of the engine output reducing means 111 such that thereduction of the output power of the engine 13 may be increased as theengine speed represented by an engine speed detection signal from theengine speed detecting section 110 increases, but sets, when an abnormalcondition detection signal is developed and the range detection signalindicates the running range, a control amount of the engine outputreducing means 111 such that the reduction of the output power of theengine 13 may be decreased as the accelerator pedal operation amountrepresented by an operation amount detecting signal from the operationamount detecting means 102 increases.

It is to be noted that, in case the engine output reducing means 111employed in the vehicle engine controlling system 1 is of the type whichadjusts the amount of air to flow through a bypass passage whichbypasses the throttle valve 31, the output reduction control amountsetting means 112 may include, as shown in FIG. 2 (ii), an air amountjudging section 112a for comparing, when an abnormal detection signal isdeveloped from the abnormal condition detecting means 105, an actualcontrol amount of the throttle valve 31 with a control amount set by thethrottle valve control amount setting means 103 and developing, when theactual control amount is smaller than the set control amount by anamount greater than a predetermined value, an air amount shortage signalbut developing an air amount surplus signal when the actual controlamount is greater than the set control amount by an amount greater thanthe predetermined value, and an opening/closing controlling section 112bfor opening or closing the bypass passage 52 in response to an output ofthe air amount judging section 112a.

Subsequently, the vehicle engine controlling system of the presentembodiment will be described more in detail with reference to a blockdiagram of FIG. 2 which schematically shows general construction of thevehicle engine controlling system 1.

The vehicle engine controlling system 1 shown includes a treadled amountdetecting section 14, the accelerator switch 15, a brake switch 16, ashift selector switch 17, an automatic cruise switch 18, a car weightdetecting section 19, an intake air amount detecting section 20, anengine rotational speed detecting section 21, an output shaft rotationalspeed detecting section 22, a gear position detecting section (gearposition detecting means and kick-down drum rotation condition detectingmeans) 23, a speed/acceleration detecting section 24, a control section25 for developing a control signal in accordance with input signalsreceived from the detecting sections 19 to 24 and the switches 14 to 18,a throttle valve pivoting section 26 for actuating a throttle valve 31in response to a control signal received from the control section 25,and a car body advancing direction acceleration sensor (G sensor) 51 fordirectly detecting an acceleration of a car body in the advancingdirection.

The individual components will be described below.

The treadled amount detecting section 14 is provided for detecting atreadled amount of the accelerator pedal 27 in order to artificiallyadjust the output power of the engine. The treadled amount detectingsection 14 includes, as shown in FIG. 3, a potentiometer 37 responsiveto the accelerator pedal 27 for developing a voltage which increases inproportion to a treadled amount of the accelerator pedal 27, and ananalog to digital (A-D) converter 38 for converting a value of an outputvoltage of the potentiometer 37 into an accelerator pedal treadledamount APS of a digital value.

The accelerator switch 15 is turned on or off in response to theaccelerator pedal 27. In particular, when the accelerator pedal 27 isnot treadled, the accelerator switch 15 is on, but when the acceleratorpedal 27 is treadled, the accelerator switch 15 is off.

The brake switch 16 is turned on or off in response to a brake pedal 28which is provided for artificially operating a brake (not shown) forbraking the vehicle. When the brake pedal 28 is treadled, the brakeswitch 16 is on, and when the brake pedal 28 is not treadled, the brakeswitch 16 is off.

The shift selector switch 17 develops a digital signal indicative of anoperating condition of an automatic transmission 32 which isartificially designated by a shift selector 29. Such operating conditionof the automatic transmission 32 is one of an N range for a neutralcondition, a P range for parking, a D range for driving in automaticgear change, an L range when the automatic transmission 32 is held atits low gear position, and an R range for rearward movement. It is to benoted that the P range is sometimes represented as included in the Nrange.

The automatic cruise switch 18 is provided for artificially designatinga running condition of the vehicle, but also functions as anacceleration instructing means for providing an accelerating ordecelerating instruction to the vehicle. Referring to FIG. 6, theautomatic cruise switch 18 includes a main lever 18a providedprojectingly on a side of a steering column 49 and having functions asan acceleration switch 45 and a changing over switch 46, a throttleswitch 47 mounted for sliding leftward and rightward movement in FIG. 6on the main lever 18a, and an aimed speed changing switch 48 mounted forturning movement around the main lever 18a. The automatic cruise switch18 will be hereinafter described in detail.

Referring back to FIG. 2, the car weight detecting section 19 isprovided for detecting a weight of the vehicle in accordance with achange in relative position between a wheel and a car body, that is, achange in height of the vehicle to develop a detection value as adigital value.

The intake air amount detecting section 20 is provided for detecting anamount of air sucked into the engine 13 through an intake air path 30 todevelop a detection value as a digital value.

The engine rotational speed detecting section 21 is provided on acamshaft (not shown) of the engine 13 for detecting a rotational speedof the engine 13 to develop a detection value as a digital value.

The output shaft rotational speed detecting section 22 is provided on anoutput shaft (not shown) of a torque converter (not shown) of theautomatic transmission 32 to develop a detection value as a digitalvalue. It is to be noted that reference numerals 33 and 34 in FIG. 2denote a left front wheel and a right front wheel, respectively, whichare driven by the engine 13 by way of the automatic transmission 32.

The gear position detecting section 23 is provided for detecting acurrent gear position of the automatic transmission 32 in response to aspeed changing instruction signal developed from a gear shiftinginstructing section (not shown) provided in the automatic transmission32 to develop a detection value as a digital value. Further, the gearposition detecting section 23 can provide an output of kick-down drumrotation condition information of the automatic transmission 32.

The speed/acceleration detecting section 24 is provided for detecting anactual running speed of the vehicle and an actual acceleration of thevehicle to develop detection values as digital values, and theaforementioned running speed detecting section 124 corresponds to thespeed/acceleration detecting section 24. Referring to FIG. 5, thespeed/acceleration detecting section 24 includes a right rear wheelspeed detecting section 42 for detecting a speed of the right rear wheel36 to develop a detection value as a digital value, a left rear wheelspeed detecting section 43 for detecting a speed of the left rear wheel35 to develop a detection value as a digital value, and aspeed/acceleration calculating section 44 for calculating an actualspeed and an actual acceleration of the vehicle in accordance withdigital values received from the right rear wheel speed detectingsection 42 and the left rear wheel speed detecting section 43.

Referring back to FIG. 2, the control section 25 includes a runningcondition designating section 3, an aimed acceleration setting section4, a final aimed speed setting section 6, a final aimed speedmodification controlling section 6a, a constant speed controllingsection 8, an acceleration controlling section 9, a decelerationcontrolling section 10, a final condition detecting section 11, and arunning condition changing over section 12. Though not shown in FIG. 2,the control section 25 further includes the throttle valve controlamount setting section 103 and the output reduction control amountsetting means 112.

Consequently, in the control section 25, if constant speed running isdesignated by the running condition designating section 3, then athrottle opening necessitated for required constant speed running is setby the constant speed controlling section 8. On the other hand, ifaccelerated running is designated, then a throttle opening necessitatedfor required accelerated running is set by the acceleration controllingsection 9, but on the contrary if decelerated running is designated,then a throttle opening necessitated for required decelerated running isset by the deceleration controlling section 10. The magnitude of athrottle opening set in this manner is delivered as a digital signal tothe throttle valve pivoting section 26.

The throttle valve pivoting section 26 pivots the throttle valve 31 sothat the throttle valve 31 may assume a throttle opening set by thecontrol section 25. Referring to FIG. 4, the throttle valve pivotingsection 26 includes an actuator driving section 39 responsive to asignal from the throttle valve control amount setting means 103 of thecontrol section 25 for developing a driving signal for pivoting thethrottle valve 31 to a set opening, a throttle valve actuator 40 forpivoting the throttle valve 31 in response to a signal from the actuatordriving section 39, and a throttle valve opening detecting section 41for detecting an opening of the throttle valve 31 pivoted by thethrottle valve actuator 40 and for feeding the detection value of theopening as a digital value to the actuator driving section 39. It is tobe noted that the throttle valve actuator 40 may be an electric motorsuch as a stepper motor.

The throttle valve 31 is mounted for pivotal motion in the intake airpath 30. The throttle valve 31 is thus adjusted to a suitable angularposition to open or close the intake air path 30 (adjust the opening) toadjust the intake air amount to the engine 13.

It is to be noted that the engine 13 shown has a bypass passage 52provided for the intake air path 30, and an ignition speed controller(ISC) 53 is interposed in a parallel relationship to the throttle valve31 in the bypass passage 52. The ISC 53 cooperates with the throttlevalve 31 to adjust the flow rate of intake air to control the enginespeed upon idling of the engine 13 and includes a control valve 53a anda valve actuating section 53b for actuating the control valve 53a. Thevalve actuating section 53b can actuate the control valve 53a to apredetermined opening in response to an instruction from the controlsection 25.

The car body advancing direction acceleration sensor 51 is a so-called Gsensor which detects whether or not the acceleration of a car body inthe advancing direction has presented a change but does not detect adetailed acceleration value. In particular, the car body advancingdirection acceleration sensor 51 is provided so as to detect, in case anacceleration detected by the speed/acceleration detecting section 24 haspresented a change, such change independently of the speed/accelerationdetecting section 24 in order that data in error arising from adisturbance at or an error in detection or the like by thespeed/acceleration detecting section 24 may not inadvertently be takenas data into the control section 25.

Here, the automatic cruise switch 18 will be described in detail withreference to FIG. 6.

The acceleration switch 45 is changed over by pivoting the main lever18a around the steering column 49. Here, the acceleration switch 45 canbe changed over between such four positions [a], [b], [c] and [d] asshown in FIG. 6 and presents an on-state at each of the four positions.When the acceleration switch 45 is at the position [a], the vehicle iscontrolled to run at a designated speed in a constant speed runningcondition, but when the acceleration switch 45 is at one of the otherpositions [b], [c] and [d], the vehicle is controlled to run at anindividual aimed acceleration in an accelerated running condition. Asthe acceleration switch 45 is changed over to [b]→[c]→[d], the value ofthe aimed acceleration increases, and at the position [b], the vehicleis controlled to run at a comparatively low acceleration; at theposition [c], the vehicle is controlled to run at a medium acceleration;and at the position [d], the vehicle is controlled to run at acomparatively high acceleration.

The changing over switch 46 serves as a running condition change-overoperating means and is turned on by pulling the main lever 18a forwardlyto change over a running condition of the vehicle in accordance with aposition of the acceleration switch 45. If the hand is released from themain lever 18a after such changing over is made, the lever 18a isautomatically returned to its initial position.

For example, when the acceleration switch 45 is at the position [a], therunning condition of the vehicle is changed over between constant speedrunning and decelerated running by the changing over switch 46. Inshort, if the changing over switch 46 is operated when the accelerationswitch 45 is at the position [a] and the vehicle is running at aconstant speed, then the running condition of the vehicle is changedover from constant speed running to decelerated running. On thecontrary, if the changing over switch 46 is operated when theacceleration switch 45 is at the position [a] and the vehicle is runningin deceleration, the running condition is changed over from deceleratedrunning to constant speed running.

To the contrary, when the acceleration switch 45 is at the position [b],[c] or [d], the running condition of the vehicle is changed over betweenaccelerated running and constant speed running by the changing overswitch 46. In short, if the changing over switch 46 is operated when theacceleration switch 45 is at the position [b], [c] or [d] and thevehicle is 10 running in acceleration, the running condition is changedover from accelerated running to constant speed running. To thecontrary, if the changing over switch 46 is operated when theacceleration switch 45 is at the position [b], [c] or [d] and thevehicle is running at a constant speed, the running condition is changedover from constant speed running to accelerated running.

Further, the final aimed speed can be changed by the changing overswitch 46. In particular, if the changing over switch 46 is turned andthen kept on in order to change over the running condition of thevehicle from constant speed running to accelerated running, the finalaimed speed is increased in proportion to the duration of the on-stateof the changing over switch 46. To the contrary, if the changing overswitch 46 is turned and then kept on in order to change over the runningcondition from constant speed running to decelerated running, the finalaimed speed is decreased in proportion to the duration of the on-stateof the changing over switch 46.

The throttle switch 47 is provided for changing contents of control overthe throttle valve 31 in accordance with a condition of the acceleratorpedal 27 or the brake pedal 28. The throttle switch 47 is changed overbetween three positions [e], [f] and [g] and presents an on-state ateach of the three positions.

When the throttle switch 47 is at the position [e], control is effectedin such a relationship wherein the accelerator pedal 27 and the throttlevalve 31 are mechanically coupled directly to each other. Thus, thethrottle valve 31 is adjusted in proportion to movement of theaccelerator pedal 27.

To the contrary, when the throttle switch 47 is at the position [f] or[g], the accelerator pedal 27 and the throttle valve 31 do not present amechanically directly coupled condition and are controlled in thefollowing manner.

In short, when the throttle switch 47 is at the position [f], if thebrake pedal 28 is treadled to effect deceleration and then released,such control is effected till subsequent treadling of the acceleratorpedal 27 that the throttle valve 31 may maintain a minimum openingthereof corresponding to an idling position of the engine 13.

When the throttle switch 47 is at the position [g], if the brake pedal28 is treadled to effect deceleration and then released, such control ofopening of the throttle valve 31 is executed until either theaccelerator pedal 27 is treadled subsequently or the acceleration switch45 or the changing over switch 46 is manually operated to designateaccelerated running or decelerated running that the speed of the vehicleupon releasing of the brake pedal 28 may be maintained to make constantspeed running of the vehicle except when the vehicle during running isto be stopped.

The aimed speed changing over switch 48 is provided for modifying a setvalue of an aimed speed for constant speed running of the vehicle. Theaimed speed changing over switch 48 is turned on when it is turnedupwardly (in the direction indicated by the mark (+) in FIG. 6) ordownwardly (in the direction indicated by the mark (-) in FIG. 6), andif the hand is released from the switch 48 after such changing over iscompleted, then the switch 48 is automatically returned to its initialposition (a neutral position shown in FIG. 6) at which it presents anoff-state. If the aimed speed changing over switch 48 is operated to anon-state on the (+) side, the final aimed speed is increased inproportion to the duration of the on-state. To the contrary, if theaimed speed changing over switch 48 is operated to an on-state on the(-) side, the final aimed speed is decreased in proportion to theduration of the on-state. Thus, if the aimed speed changing over switch48 is turned to increase or decrease the final aimed speed and then thehand is released from the switch 48, the final aimed speed is set to avalue at a point of time when the hand is released.

It is to be noted that an electric circuit of a connecting portionbetween the automatic cruise switch 18 and the control section 25 hassuch a construction as shown in FIG. 7.

Referring to FIG. 7, the control section 25 includes a plurality ofbuffers BU1 to BU10 at which it receives signals, and a plurality ofpull-up resistors R1 to R10 provided on the input sides of the buffersBU1 to BU10, respectively. The pull-up resistors R1 to R10 are connectedin parallel to each other to a power source 50 for the buffers BU1 toBU10.

Different contacts of the acceleration switch 45, changing over switch46, throttle switch 47 and aimed speed changing switch 48 whichconstitute the automatic cruise switch 18 are individually connected toinput terminals of the buffers BU1 to BU10.

It is to be noted that the marks [a] to [d] applied to the individualcontacts of the acceleration switch 45 in FIG. 7 correspond to thepositions [a] to [d] shown in FIG. 6, respectively, and the contact (ON)of the changing over switch 46 is a contact which makes when the mainlever 18a is pulled forwardly to an on position. Meanwhile, the marks[e] to [g] applied to the individual contacts of the throttle switch 47correspond to the positions [e] to [g] in FIG. 6, respectively, and themarks (+) and (-) applied to the individual contacts of the aimed speedchanging switch 48 are contacts which make when the aimed speed changingswitch 48 is manually operated to turn to the (+) side or the (-) sidein FIG. 6, respectively.

At the input terminals of those ones of the buffers BU1 to BU10 whichare connected to those contacts of the switches which are in anon-state, electric current flows from the power source 50 for thebuffers BU1 to BU10 to the pull-up resistors R1 to R10 connected to theinput terminals. Consequently, a low level digital signal is provided toeach of those buffers connected to the contacts which are in anon-state. Meanwhile, a high level digital signal is provided to each ofthose buffers connected to the other contacts which are in an off-state.

Accordingly, when the contacts are, for example, in such a connectingcondition as shown in FIG. 7, a low level digital signal is supplied tothe input terminals of the buffers BU1 and BU7 of the control section 25while a high level digital signal is supplied to the input terminals ofthe buffers BU2 to BU6 and BU8 to BU10.

Contents of control by the engine controlling device 1 will be describedin detail below.

FIGS. 8(i) to 18 are flow charts illustrating contents of control by theengine controlling device, and FIG. 8(i) is a main flow chartillustrating contents of main operation of the present control. Whilethe control is executed in accordance with the main flow chart, it isperiodically interrupted by such interrupt controls as illustrated inFIGS. 8(ii) to 8(iv).

FIG. 8(ii) is a flow chart illustrating contents of interrupt control(hereinafter referred to as first interrupt control) which is executedpreferentially by an interrupt for each 50 milliseconds while the maincontrol shown in FIG. 8(i) is being executed and which is executed inresponse to a counter CAPCNG.

FIG. 8(iii) is a flow chart illustrating contents of interrupt control(hereinafter referred to as second interrupt control) which is executedpreferentially by an interrupt for each 10 milliseconds similarly duringexecution of the main control shown in FIG. 8(i) in order to find out,in response to an accelerator pedal treadled amount APS detected by thetreadled amount detecting section 11, a changing rate DAPS of thetreadled amount APS.

FIG. 8(iv) is a flow chart illustrating contents of interrupt control(hereinafter referred to as third interrupt control) which is executedpreferentially by an interrupt for each 65 milliseconds similarly duringexecution of the main control shown in FIG. 8(i) in order to find out anactual speed VA and an actual acceleration DVA of the vehicle inaccordance with a right rear wheel speed VARR detected by the right rearwheel speed detecting section 42 of the speed/acceleration detectingsection 24 and a left rear wheel speed VARL detected by the left rearwheel speed detecting section 43. The control is executed by thespeed/acceleration calculating section 44.

Meanwhile, FIGS. 8(v) and 8(vi) are flow charts each showing contents offail safe control for compensating for an error in actual accelerationDVA found out by the third interrupt control shown in FIG. 8(iv). Inshort, while in the third interrupt control an actual acceleration DVAis calculated using a detection value obtained by the speed/accelerationdetecting section 24, since a speed of the vehicle is detected from aspeed of a wheel by the speed/acceleration detecting section 24, if abump, a rebound or the like should take place at the wheel 35 or 36 dueto an uneven condition of a road surface, then there is the possibilitythat a value which is instantaneously different from an actual speed VAmay be detected as a car speed. Thus, the fail safe control of FIG. 8(v)is executed in order to prevent an actual acceleration DVA from beingcalculated from such erred car speed data arising from such a bump, arebound or the like. Here in the present embodiment, the fail safecontrol is executed relying upon a detection value of a device (notshown) for detecting an air pressure of an air suspension which isprovided as one of the car weight detecting section 19. A change in airpressure is thus employed as a scale of reliability of a measured valueas an actual speed VA because, when an error takes places in a wheelspeed due to a bump, a rebound or the like, the air pressure of the airsuspension changes simultaneously.

Meanwhile, the fail safe control of FIG. 8(vi) is a control for judgingit from detection data obtained by direct detection of an accelerationof the vehicle in its advancing direction by means of the G sensor 51whether or not there is an error in value of the actual acceleration DVAand for executing suitable processing in accordance with a result ofsuch judgment. By the control, any error in acceleration vale whicharises from any cause can be judged widely irrespective of whether thecause is a bump, a rebound or the like, and can be dealt withappropriately.

Further, FIG. 8(vii) is a flow chart illustrating a procedure of settingcar weight data which is executed at the control section 25 in responseto a weight of the vehicle detected by the car weight detecting section19.

While control of various contents is executed in the main control shownin FIG. 8(i), details of contents of the control are illustrated inFIGS. 9 to 18.

FIG. 9 is a flow chart illustrating details of control of directthrottle movement executed at step A117 of FIG. 8(i). The directthrottle movement control is control of the engine 13 by control of thethrottle valve 31 by way of the accelerator pedal 27 in such arelationship that the accelerator pedal 27 and the throttle valve 31 aremechanically coupled directly to each other.

FIG. 10 is a flow chart illustrating details of control of non-directthrottle movement executed at step A116 of FIG. 8(i). The non-directthrottle movement control is control of the engine 13 by control of thethrottle valve 31 in such a manner that the accelerator pedal 27 and thethrottle valve 31 do not always have a mechanically directly coupledrelationship.

FIG. 11 is a flow chart illustrating details of accelerator mode controlexecuted at step C137 of FIG. 10. The accelerator mode control iscontrol of the engine 13 by determining an aimed acceleration of thevehicle in accordance with an accelerator pedal treadled amount APSdetected by the treadled amount detecting section 14, an acceleratorpedal treadled amount changing rate DAPS calculated by the controllingsection 22 in accordance with the treadled amount APS and a value of thecounter CAPCNG and by pivoting the throttle valve 31 so as to obtain anoutput power of the engine 13 with which the aimed acceleration will beattained.

FIG. 12 is a flow chart illustrating details of automatic cruise modecontrol executed at step C144 of FIG. 10. The automatic cruise modecontrol is control of the engine 13 to place the vehicle into anaccelerated running condition, a decelerated running condition or aconstant speed running condition by setting an opening of the throttlevalve 31 by the acceleration controlling section 9, the decelerationcontrolling section 10 or the constant speed controlling section 8 ofthe control section 25 in accordance with information from the detectingsections 14 and 19 to 24 and the switches 15 to 18 of FIG. 2 when theaccelerator pedal 27 and the brake pedal 28 are not in a treadledcondition and by pivoting the throttle valve 31 by the throttle valvepivoting section 26.

FIG. 13 is a flow chart illustrating details of changing over switchcontrol executed at step E128 of FIG. 12. The changing over switchcontrol is executed in relation to designation of a running condition ofthe vehicle by the running condition designating section 3 of thecontrol section 25, to changing over by the changing over switch 46 andthe running condition changing over section 12 of the control section25, to setting of a final aimed speed by the final aimed speed settingsection 6 of the control section 25 and also to modification of thefinal aimed speed by the final aimed speed modification controllingsection 6a of the control section 25.

FIG. 14 is a flow chart illustrating details of acceleration switchcontrol executed at step E121 of FIG. 12. The acceleration switchcontrol is control of setting of an aimed acceleration DVS₂ which isexecuted, when the acceleration switch 45 is changed over to one of thepositions [b] to [d] in FIG. 6, in accordance with the thus changed overposition of the acceleration switch 45 by the aimed acceleration settingsection 4 of the control section 25. The aimed acceleration DVS₂ is anaimed value of an acceleration which becomes fixed after the vehiclestarts acceleration as a result of operation of the acceleration switch45 or the changing over switch 46 to change over the designation of therunning condition designating section 3 of the controlling section toaccelerated running.

FIG. 15 is a flow chart illustrating details of deceleration controlexecuted at step E131 of FIG. 12. The deceleration control is suchcontrol that, when the designation of the running condition designatingsection 3 of the control section 25 is changed over to deceleratedrunning by operation of the acceleration switch 45 or the changing overswitch 46, decelerated running may be effected at a deceleration whichcan be realized and is nearest to a negative aimed acceleration (thatis, an aimed deceleration) set by the aimed acceleration setting section4 of the control section 25. The deceleration control is executed mainlyby the deceleration controlling section 10 and the aimed accelerationsetting section 4 of the control section 25.

FIG. 16 is a flow chart illustrating details of aimed speed controlexecuted at step E133 of FIG. 12. The aimed speed control is executed inorder to attain, when the designation by the running conditiondesignating section 3 of the control section 25 is changed over toconstant speed running by operation of the acceleration switch 45 or thechanging over switch 46 or the like, constant speed running wherein therunning speed of the vehicle is maintained at an equal value to therunning speed at a point of time when the designation is changed over toconstant speed running and in order to modify the aimed value of arunning speed for aimed constant speed running by means of the aimedspeed changing switch 48. The aimed speed control is executed mainly bythe constant speed controlling section 8 of the control section 25.

FIG. 17 is a flow chart illustrating details of acceleration controlexecuted at step E122 of FIG. 12. The acceleration control is controlwhich is executed in order to make a change (increase or decrease) inacceleration smooth. For example, when the designation by the runningcondition designating section 3 of the control section 25 is changedover to accelerated running by operation of the acceleration switch 45or the changing over switch 46, an increase or decrease in accelerationof the vehicle to an aimed acceleration set by the aimed accelerationsetting section 6 of the control section 25 in accordance with theposition of the acceleration switch 45 is made smooth, or a change inacceleration when the running speed of the vehicle reaches, as a resultof accelerated running, a final aimed speed set by the final aimed speedsetting section 6 and the final aimed speed modification controllingsection 6a of the control section 25 is made smooth.

FIG. 18 is a flow chart illustrating details of control of determinationof an aimed acceleration DVS₄ executed at step J115 of FIG. 16. Theaimed acceleration DVS₄ is an aimed value of an acceleration of thevehicle for maintaining the running speed of the vehicle at a valueequal to an aimed speed when the designation by the running conditiondesignating section 3 of the control section 25 is constant speedrunning.

FIGS. 19 to 26 are graphs illustrating relationships between parametersof maps used for control by the engine controlling system 1 andvariables read out in accordance with the parameters.

FIGS. 27(i) and 27(ii) are graphs showing exemplary changes of an aimedacceleration and a running speed with respect to an interval of timeelapsed after the acceleration switch 45 is changed over to change thedesignation by the running condition designating section 3 of thecontrol section 25 to accelerated running.

FIGS. 28(i) to 30 illustrate control of the automatic transmission 32 bythe automatic transmission controlling device (not shown). Of FIGS.28(i) to 30, FIGS. 28(i) to 28(v) are flow charts illustratingdown-shift control which is executed when the speed of the vehiclecannot be maintained only by control of the engine such as, for example,upon riding on an upward slope or on a downward slope during constantspeed control in automatic cruise mode control, and a cycle ofdown-shift control is achieved by continuously executing procedures ofFIGS. 28(i) to 28(iii). The down-shift control is interrupt controlexecuted for each 20 milliseconds, and FIGS. 28(i) and 28(ii) mainlyrelate to control upon riding on an upward slope while FIG. 28(iii)mainly relates to control upon riding on a downward slope. Meanwhile,FIGS. 28(iv) and 28(v) show a modification to the control upon riding ona downward slope shown in FIG. 28(iii).

Meanwhile, FIGS. 29(i) to 29(iii) illustrate down-shift control of theautomatic transmission 32 which is executed, when quick braking isperformed by way of the brake pedal 28, so as to render the engine brakeeffective to achieve quick deceleration of the vehicle. Particularly,FIG. 29(i) is a flow chart illustrating contents of control of a maincontrol; FIG. 29(ii) is a flow chart illustrating contents of control ofan interrupt control which is executed in 20 ms timer interrupt to themain control; and FIG. 29(iii) is a map which is used in the 20 ms timerinterrupt control to find out time data therefrom.

It is to be noted that those down-shift controls are executed by adown-shift controlling section (not shown) in accordance with data of anactual speed VA and an actual acceleration DVA detected by thespeed/acceleration detecting section 24, an aimed speed VS set by thefinal aimed speed setting section 6, a current engine speed DRPMdetected by the engine speed detecting section 21, a current gearposition detected by the gear position detecting section 23 and soforth.

Further, FIG. 30 is a map showing an example of setting a pseudotreadled amount SFTAPS which is used as a control parameter with whichthe automatic transmission 32 is to be control to change the gearposition in an ordinary manner when automatic cruise mode control isbeing executed with the accelerator pedal 15 held in a releasedcondition.

In addition, FIGS. 31(i) to 36 relate to speed change shock reducingcontrol upon shifting of the gear position of the automatic transmission32. In the speed change shock reducing control, the throttle opening ofthe engine 13 is temporarily reduced to restrict the variation of torqueof the output shaft of the automatic transmission 32 in order tomoderate a shock upon shifting of the gear position of the automatictransmission 32. Particularly, in the present control, the timing ofstarting of a closing movement of the throttle valve 31 is determined inresponse to a condition of rotation of the kick-down drum.

Of those figures, FIGS. 31(i) to 31(iv) are flow charts illustratingcontents of the control, and FIG. 31(i) relates mainly to control uponup-shifting from the first to the second gear position or from thesecond to the third gear position; FIG. 31(ii) relates to control uponup-shifting from the third to the fourth gear position; FIG. 31(iii)relates to setting of a throttle opening in any of the shock reducingcontrols; and FIG. 31(iv) shows 5 ms interrupt control in thosecontrols. Meanwhile, FIGS. 32(i) to 32(iii) and 33(i) to 33(iii) aretime charts illustrating speed change shock reducing control, and FIGS.34 to 36 are maps for use in the speed change shock reducing control.

FIGS. 37(i) to 39 illustrate throttle actuator fail control for allowingtorque adjustment to be executed within an allowable range when thethrottle actuator 40 of the throttle valve pivoting section 26 enters afail condition. Particularly, FIGS. 37(i) and 37(ii) are flow chartsillustrating contents of such control, and FIG. 37(i) relates to a maincontrol while FIG. 37(ii) relates to control to be executed in 10 msinterrupt to the main control. Meanwhile, FIGS. 38 and 39 are maps whichare used in such control.

Operation of the engine controlling system 1 having such a constructionas described hereinabove will be described below with reference to FIGS.1(i) to 39.

At first, if an ignition switch (not shown) of the vehicle is turned onto start the engine 13, a crankshaft (not shown) of the engine 13 startsto be rotated by a starter motor (not shown), and an amount of fuelnecessary for starting of the engine 13 determined by a fuel controllingdevice (not shown) is supplied into the engine 13 by a fuel injectiondevice (not shown). Meanwhile, fuel is ignited by an ignition device(not shown) at a timing determined by an ignition timing controllingdevice (not shown). Consequently, the engine 13 starts its operation byitself.

Simultaneously, a power source is connected to the engine controllingsystem 1 to start control of the engine 13 in accordance with the flowcharts shown in FIGS. 8(i) to 18.

The control will be described in detail below.

At first at step A101 of FIG. 8(i), various variables, flags, timers andcounters which are used in the control are all reset so that they mayhave a value of zero, and then the sequence advances to step A102.

In this instance, in preference to the control of the main flow shown atsteps A101 to A117 of FIG. 8(i), the first, second and third interruptcontrols are executed. The first interrupt control is executed for each50 milliseconds in accordance with the flow chart of steps A118 to A120of FIG. 8(ii). The second interrupt control is executed for each 10milliseconds in accordance with the flow chart of steps A121 to A122 ofFIG. 8(iii). The third interrupt control is executed for each 65milliseconds in accordance with the flow chart of steps A123 to A128 ofFIG. 8(iv).

Among the interrupt controls, the first interrupt control is executed bythe control section 25 and is an interrupt control entered in responseto the counter CAPCNG as mentioned hereinabove. In short, at a timedirectly after control by the engine controlling system 1 is started,the value of the counter CAPCNG is 0 as a result of resetting at stepA101, and accordingly, if the counter CAPCNG is incremented by one atstep A118, then the value of the counter CAPCNG will be 1. As a result,the requirement of CAPCNG=1 at subsequent step A119 as met, andconsequently the sequence advances to step A120. At step A120, thecounter CAPCNG is decremented by one and now has a value equal to 0.

Then, when the first interrupt control is started again after lapse of50 milliseconds, the value of the counter CAPCNG is 0 similarly as atthe time of starting of the preceding execution of the first interruptcontrol as described above. Accordingly, contents of the control for thepresent time will be quite the same as those of the first interruptcontrol for the preceding time, and consequently, the counter CAPCNGwill have a value equal to 0 again when the first interrupt control forthe present time is completed. In short, unless the counter CAPCNG isset to a value other than zero at any step of the control of the mainflow, the first interrupt control which is executed for each 50milliseconds is repeated with the quite same contents, and the resultedvalue of the counter CAPCNG always remains 0.

The second interrupt routine is executed by the control section 25. Herein the second interrupt control, a changing rate DAPS of an acceleratorpedal treadled amount APS detected by the treadled amount detectingsection 14 is found out in response to such treadled amount APS. It isto be noted that the value of an accelerator pedal treadled amount APSis a value which is obtained by converting a voltage, which is developedfrom the potentiometer 37 of the treadled amount detecting section 14interlocked with the accelerator pedal 27 and increases in proportion toa treadled amount of the accelerator pedal 27, into a digital value bythe analog to digital converting section 38 of the treadled amountdetecting section 14.

In the second interrupt control, an accelerator pedal treadled amountAPS is read in at step A121, and then at step A122, a difference betweenthe value APS thus read in and another accelerator pedal treadled amountAPS' which was read in 100 milliseconds ago in a similar manner andstored in the control section 25, that is, |APS-APS'|, is calculated asa value DAPS. Since the interrupt control is repeated for each 10milliseconds, the values APS, APS' and DAPS are updated for each 10milliseconds.

The third interrupt control is executed by the speed/accelerationdetecting section 24 to calculate an actual speed VA and an actualacceleration DVA.

After starting of the third interrupt control, at first at step A123, awheel speed of the right rear wheel 36 detected by the right rear wheelspeed detecting section 42 is read in as VARR, and then at step A124, awheel speed of the left rear wheel 35 detected by the left rear wheelspeed detecting section 43 is read in as VARL. Then at step A125, anaverage of the values VARR and VARL is calculated and stored as anactual speed VA of the vehicle. Subsequently at step A126, a variationof the actual speed VA calculated at step A125 from another actual speedVA' which was calculated and stored in a similar manner in the precedinginterrupt control executed 90 milliseconds before the present interruptcontrol, that is, VA-VA', is calculated as an actual acceleration DVS₆₅.Then at step A127, a variation of an average value VAA between VA andVA' from an average value VAA' between VA' and a further actual speedVA" which had been calculated and stored in a similar manner in thefurther preceding interrupt control executed further 390 millisecondsbefore the interrupt control in which VA' was calculated, that is,VAA-VAA', is calculated and stored as an actual acceleration DVA₁₃₀.Further at step A128, an average of the actual acceleration DVA₁₃₀calculated at step A127 and four latest actual accelerations DVA₁₃₀calculated in a similar manner in the preceding interrupt controls iscalculated as an actual acceleration DVA₈₅₀.

The values VA, VA', VA", VAA, VAA', DVA₆₅, DVA₁₃₀ and DVA₈₅₀ calculatedin this manner are updated for each 65 milliseconds because the thirdinterrupt control is executed for each 65 milliseconds.

Since the value DVA₆₅ among the actual accelerations is calculated inaccordance with the two actual speeds VA and VA' as described above, thefollow-up performance to an actual change in acceleration of the vehicleis at the highest, but, the influence when an error of an actual speedis increased by a disturbance or the like is great and accordingly thestability is low. To the contrary, since the value DVA₈₅₀ is calculatedfrom five actual accelerations DVA₁₃₀ which are each calculated inaccordance with three actual speeds VA, VA' and VA" as described above,the influence of a disturbance is small and the stability is highcontrary to the value DVA₆₅, but the follow-up performance is low. Onthe other hand, the value DVA₁₃₀ has an intermediate stability and anintermediate follow-up performance between the values DVA₆₅ and DVA₈₅₀.

Here, contents of the fail safe control executed to compensate for anerror in actual acceleration DVA found out by the third interruptcontrol will be described with reference to FIG. 8(v). In particular, atfirst at step N101, it is detected whether or not a change in detectionvalue detected by the air pressure detecting device for the airsuspension provided as one of components of the car weight detectingsection 19, that is, a rate of change in air pressure, is greater than apreset reference value.

When the change in detection value is not greater than the referencevalue, it is determined that no error is involved in a measured value ofthe actual speed VA, and the sequence advances to step N108 at which thevalue of a flag I₁₄ is reset to 0 and then to step N109 at which a timerTMA' is reset, whereafter the sequence advances to step N110. At stepN110, actual accelerations DVA₆₅, DVA₁₃₀ and DVA₈₅₀ are calculated in anormal manner in accordance with the steps A126 to A128 describedhereinabove.

It is to be noted that, in case the condition wherein a change indetection value is not greater than the reference value continues from astage before the fail safe control is executed, the flag I₁₄ remains 0from the first, and the timer TMA' is already in a reset state.

The flag I₁₄ indicates a value equal to 1 when the change in airpressure of the air suspension is already greater than the referencevalue. Meanwhile, the timer TMA' is provided to count a duration while achange in air pressure of the air suspension continues to remain greaterthan the preference value.

To the contrary, in case the change in detection value is greater thanthe reference value, it can be judged at step N101 that an error hastaken place in a measured value of the actual speed VA. In thisinstance, the sequence advances at first to step N102 at which it isjudged whether or not the value of the flag I₁₄ is equal to 1.

Now, if it is assumed that the change in air pressure of the airsuspension has become greater than the reference value for the firsttime, then since the value of the flag I₁₄ still remains equal to 0, thesequence advances to step N103 at which the value of the flag I₁₄ ischanged to 1 and then to step N104 at which counting of the timer TMA'is started. Subsequently at step N105, calculations of actualaccelerations DVA₆₅, DVA₁₃₀ and DVA₈₅₀ are stopped, and calculatedvalues obtained immediately before then (final calculated values) arestored as output data.

Subsequently, the sequence advances to step N106 at which a controlcycle is re-set. Such re-setting of a control cycle signifies returningof the control shown in the main flow of FIG. 8(i) which will behereinafter described to its initial state, that is, to the stage ofstep A101 to start a new control cycle. After then, the sequenceadvances to step N107.

To the contrary, in case it was judged in the preceding control cyclethat the change in air pressure of the air suspension was greater thanthe reference value, the flag I₁₄ already assumes a value equal to 1.Consequently, it is judged at step N102 that the value of the flag I₁₄is equal to 1. In this instance, the steps N103 to N106 are bypassed,and the sequence advances directly to step N107.

At step N107, it is judged whether or not a count value t_(TMA) ' of thetimer TMA' is greater than a predetermined value t_(c). Here, the countvalue t_(TMA) ' denotes a period of time while a condition wherein thechange in air pressure of the air suspension is greater than thereference value continues. Meanwhile, the predetermined value t_(c) is areference time and is set to a value suitably greater than a naturalperiod of oscillations of the suspension of the vehicle, for example, to750 ms or so.

Judgment at step N107 is a discrimination whether the change in airpressure of the air suspension arises from a bump, a rebound or the likeof a wheel of the vehicle or from an actual change in speed of thevehicle. In short, if the change in air pressure of the air suspensionarises from a bump, a rebound or the like of a wheel, then such changedisappears after lapse of the reference time t_(c) or so during whichthe bump, rebound or the like goes down. Accordingly, if on the contrarythe condition wherein the change in air pressure of the air suspensionis greater than the reference value continues for a period of timelonger than the reference time t_(c), then it can be regarded that theair pressure of air suspension is changing because the car speed changesactually.

In short, if the count value t_(TMA) ' of the timer TMA is greater thanthe predetermined value t_(c), then the change in air pressure arisesbecause the car speed varies actually, and it is determined that thecalculated actual acceleration data can be adopted. To the contrary, ifthe count value t_(TMA) ' of the timer TMA' is not greater than thepredetermined value t_(c), then there is the possibility that the changein air pressure of the air suspension may be caused by a bump, a reboundor the like, and it is determined that the calculated actualacceleration data cannot be adopted.

In case it is not judged at step N107 that the count value t_(TMA) ' isgreater than the predetermined value t_(c), the fail safe control comesto an end, but on the contrary if it is judged at step N107 that thecount value t_(TMA) ' is greater than the predetermined value t_(c), thesequence advances to step N108. At step N108, the value of the flag I₁₄is reset to 0, and then at step N109, the timer TMA' is reset. Afterthen, the sequence advances to step N110 at which actual accelerationsDVA₆₅, DVA₁₃₀ and DVA₈₅₀ are calculated in an ordinary manner inaccordance with the steps A126 to A128.

It is to be noted that the fail safe control executed to compensate foran error in actual acceleration DVA shown in FIG. 8(v) is repeated aftereach lapse of a predetermined interval of time which is suitably shorterthan the reference time t_(c).

Subsequently, description will be given of contents of another fail safecontrol which is executed in order to compensate for an error of anactual acceleration DVA which is calculated in the third interruptcontrol. It is to be noted that, also in the present control, in aninitial state, a flag I₁₅ is set to 0 and a timer TMA" is reset to astopping condition equal to 0.

It is to be noted that the flag I₁₅ indicates, when the value thereof isequal to 1, that there was an error in value of an actual accelerationwithin a reference period of time in a preceding control cycle orcycles. Meanwhile, the timer TMA" counts, as a count value t_(TMA) ", anelapsed time after a variation which is greater than a reference valuehas occurred in actual acceleration.

Referring to FIG. 8(vi), it is first judged at step N201 whether or notthe flag I₁₅ is equal to 1.

In case the flag I₁₅ is equal to 1, the sequence advances to step N208.However, otherwise in case there has been no error in value of an actualacceleration till the preceding fail safe control cycle, or in case someerror was judged in value of an actual acceleration in any precedingfail safe control cycle but no error has been judged in value of theactual acceleration for an interval of time longer than a reference timet_(c) ' after then, the value of the flag I₁₅ remains equal to 1.Consequently, it is judged at step N201 that the flag I₁₅ is differentfrom 1, and the sequence advances to step N202.

At step N202, it is judged whether or not the actual acceleration in thepresent control cycle presents a variation greater than the referencevalue.

If the actual acceleration does not present a greater variation than thereference value, then there is no necessity of particularly executing anoperation for the fail safe, and the sequence advances to step N211 atwhich the required actual accelerations (DVA₆₅, DVA₁₃₀ and DVA₈₅₀) arecalculated in an ordinary fashion, that is, in accordance with the stepsA126 to A128 as described hereinabove, thereby completing the presentcontrol.

In case the actual acceleration presents a greater variation than thereference value at step N202, the sequence advances to step N203 atwhich it is judged whether or not the output value of the G sensor(vehicle body advancing direction acceleration sensor) 51 presents avariation greater than a reference value.

If the output of the G sensor 51 presents a variation greater than thereference value, then this means that the actual acceleration haschanged by an amount greater than the reference value, and consequently,the data of the actual acceleration is reliable. Accordingly, thesequence advances from step N203 to step N211 at which the requiredactual accelerations (DVA₆₅, DVA₁₃₀ and DVA₈₅₀) are calculated in anordinary fashion, thereby completing the present control.

In case it is judged at step N203 that the output of the G sensor 51presents a greater variation than the reference value, this means thatthe data of the actual acceleration has changed while the actualacceleration has not actually changed by an amount greater than thereference value. Accordingly, it can be considered that some error isinvolved in the data from which a value in actual speed is to becalculated, and the actual acceleration data is not reliable.Accordingly, the sequence advances to step N204 at which the flag I₁₅ isset to 1, and then to step N205 at which a counting operation of thetimer TMA" is started.

At subsequent step N206, a calculation of the required actualaccelerations (DVA₆₅, DVA₁₃₀ and DVA₈₅₀) is stopped, and the valuescalculated in the last applicable control cycle (last calculated values)are stored as output data.

Subsequently, the sequence advances to step N207 at which a controlcycle is re-set. Re-setting of a control cycle signifies that thecontrol involved in the main flow of FIG. 8(i) which will be hereinafterdescribed is returned to the initial condition, in short, to the stageat step A101 to start a new control.

The present control cycle is completed in this manner.

After it is judged that some error has occurred in the value of theactual acceleration in this manner, it will be judged at step N201 in afollowing control cycle that the flag I₁₅ is equal to 1, andconsequently, the sequence will advance to step N208.

At step N208, it is judged whether or not the value of the count valuet_(TMA) " is greater than the reference time t_(c) '. The reference timet_(c) ' is set in advance as an interval of time, in case some error hasoccurred in calculation data of actual accelerations, until such errorhas no more influence on calculation values of the individual actualaccelerations (DVA₆₅, DVA₁₃₀ and DVA₈₅₀).

If the value of the count value t_(TMA) " is not greater than thereference time t_(c) ' at step N208, then there is the possibility thatan influence of an error in data may remain on calculated values ofactual accelerations, and accordingly, the present control is completedwithout executing calculations of actual accelerations at steps A126 toA128.

If a sufficient number of control cycles have elapsed until the value ofthe count value t_(TMA) " becomes greater then the reference time t_(c)' after it was judged that some error had occurred in value of theactual acceleration, then the value of the flag I₁₅ is set to 0 at stepN209, and then the timer TMA" is reset to 0, whereafter the sequenceadvances to step N211.

At step N211, calculations of actual accelerations at steps A126 to A128are resumed. However, in order to enter new data and execute acalculation in the present control cycle, the values stored at step N206are used until new values of actual accelerations (DVA₆₅, DVA₁₃₀ andDVA₈₅₀) are calculated after the present control cycle.

It is to be noted that also the fail safe control illustrated in FIG.8(v) and executed in order to compensate for an error of an actualacceleration DVA is repeated after each predetermined interval of time(suitable interval of time shorter than the reference time t_(C) ').

In case it is judged that the actual acceleration data are reliable inthis manner, an actual acceleration is calculated regularly, and actualacceleration data substantially equal to an acceleration at present areadopted. To the contrary, in case it is judged that an error has takenplace in an actual acceleration DVA, latest ones of already calculatedproper data (final calculated values) are adopted as data of the actualaccelerations DVA (DVA₆₅, DVA₁₃₀ and DVA₈₅₀).

In the meantime, in the main flow of steps A101 to A117 of FIG. 8(i), atstep A102 subsequent to step A101, a timer TMB for determining a timingof opening or closing of the throttle valve 31 starts its countingoperation of time, and then the sequence advances to step A103.

At step A103, various data are read in which include the actual speedVA, actual accelerations DVA₆₅, DVA₁₃₀ and DVA₈₅₀ all calculated in thethird interrupt control of steps A123 to A128 by the speed/accelerationdetecting section 24, the accelerator pedal treadled amount APS detectedby the treadled amount detecting section 14, the changing rate DAPS ofthe accelerator pedal treadled amount APS calculated by the controlsection 25 in the interrupt control of steps A121 to A122, the intakeair amount A_(E) detected by the intake air amount detecting section 20,the engine rotational speed N_(E) detected by the engine rotationalspeed detecting section 21, the car weight W detected by the car weightdetecting section 19, and the rotational speed N_(D) of a torqueconverter output shaft (not shown) of the automatic transmission 32detected by the output shaft rotational speed detecting section 22.Simultaneously, contact information of the switches including theaccelerator switch 15, brake switch 16, shift selector switch 17, andacceleration switch 45, changing over switch 46, throttle switch 47 andaimed speed changing switch 48 of the automatic cruise switch 18 andinformation of the current gear position of the automatic transmission32 detected by the gear position detecting section 23 are read in.

Subsequently at step A104, it is judged whether or not the value of aflag I₄ is equal to 1. The flag I₄ indicates, when it assumes a valueequal to 0, that constant speed running should be designated by therunning condition designating section 3 of the control section 25. Thus,at step A104, it is judged, when a constant speed running condition isto be designated, that the flag I₄ is not equal to 1 (I₄ ≠1), and thenthe sequence advances to step A105. On the contrary, when a constantspeed running condition is not to be designated, it is judged that theflag I₄ is equal to 1 (I₄ =1), and then the sequence advances to stepA107.

At step A105, it is judged whether or not another flag I₈ is equal to 1.The flag I₈ indicates, when it assumes a value equal to 0, that controlafter the speed of the vehicle has become substantially equal to anaimed speed for constant speed running should be executed in the aimedspeed control at step E133 of FIG. 12 which will be hereinafterdescribed. When it is judged at step A105 that the flag I₈ is equal to 1(I₈ =1), the sequence advances to step A107, but on the contrary when I₈=1 is not judged, the sequence advances to step A106.

At step A106, a preset fixed value T_(K) is designated as a cycle t_(K2)in which the throttle valve 31 is to be opened and closed.

At step A107, a cycle t_(K2) is defined by a product of an inversenumber of the engine rotational speed N_(E) read in at step A103 and acoefficient α of a preset fixed value. Accordingly, if constant speedrunning is designated by the running condition designating section 3 ofthe control section 25, opening or closing movement of the throttlevalve is performed in a cycle which decreases as the rotational speed ofthe engine 13 increases until the speed of the vehicle reaches an aimedcar speed in the aimed speed control, and when control is to be executedafter the speed of the vehicle has become substantially equal to theaimed speed, the throttle valve 31 is opened and closed in the fixedcycle.

At step A108 to which the sequence advances from step A106 or A107, thecycle t_(K2) is compared with an interval of time counted by the timerTMB to judge whether t_(TMB) >t_(K2) or not. Then, in case t_(TMB)>t_(K2) is judged, the sequence advances to step A109, but on thecontrary if t_(TMB) >t_(K2) is not judged, the sequence advances to stepA112.

In case t_(TMB) >t_(K2), the present control cycle falls on a timing atwhich opening or closing movement of the throttle valve 31 should beperformed. Thus, at step A109, the timer TMB is reset to change thevalue t_(TMB) to zero in order to enable determination of a timing forsubsequent next opening or closing movement of the throttle valve 31,and then at step A110, counting of time by the timer TMB is startedagain, whereafter a flag I₁₁ is changed to 1 at step A111. The flag I₁₁indicates, when it assumes a value of 1, that opening or closingmovement of the throttle valve 31 should be performed in the presentcontrol cycle after counting of time by the timer TMB has been startedagain at step A110.

To the contrary, in case t_(TMB) >t_(K2) is not judged at step A108, thepresent control cycle does not fall on a timing at which opening orclosing movement of the throttle valve 31 should be performed, andconsequently, the value of the flag I₁₁ is changed to 0 at step A112.

At step A113 to which the sequence advances from step A111 or step A112,it is judged in accordance with the contact information of the shiftselector switch 17 read in at step A103 whether or not the shiftselector 29 is at the position for the D range. In case it is judgedthat the shift selector 29 is at the position for the D range, thesequence advances to step A114, but on the contrary if it is judged thatthe shift selector 29 is at any position other than the position for theD range, the sequence advances to step A117 at which direct throttlemovement control is executed because complicated control depending upona running condition of the vehicle and so on is unnecessary.

When the sequence advances to step A114, it is judged whether or not thethrottle switch 47 of the automatic cruise switch 18 is positioned atthe position [e] shown in FIG. 6. In case the throttle switch 47 is atthe position [e], the sequence advances to step A117 at which directthrottle movement control is executed wherein the throttle valve 31 isoperated in such a manner that the throttle valve 31 is mechanicallycoupled directly to the accelerator pedal 27.

On the contrary, if it is judged at step A114 that the throttle switch47 is not at the position [e], the sequence advances to step A115. Atstep A115, it is judged whether or not the engine rotational speed N_(E)read in at step A103 is smaller than a preset reference value N_(K)(N_(E) <N_(K)) which is set a little lower than a rotational speedduring idling after completion of warming up of the engine 13. Then, incase N_(E) <N_(K) is judged, the sequence advances to step A117 in orderto execute direct throttle movement control, but if N_(E) <N_(K) is notjudged, the the sequence advances to step A116 in order to executenon-direct throttle movement control.

Accordingly, while the rotational speed of the engine 13 rises from anengine halt condition to a rotational speed in a normal condition uponstarting of the engine 13, or when the running condition of the engine13 becomes unstable by some causes so that the engine rotational speedis lowered, the throttle valve 31 operates only in accordance withmovement of the accelerator pedal 27 to control the engine 13.

The control cycle for the present time is completed with completion ofthe non-direct throttle movement control at step A116 or the directthrottle movement control at step A117, and the sequence thus returns tostep A103 in order to repeat the control of the steps A103 to A116 orA117 described above. Accordingly, in each control cycle, variousdetection values and contact information are read in and updated at stepA103, and such control as described above is executed in accordance withthe detection values and contact information.

Subsequently, the direct throttle movement control at step A117 of FIG.8(i) will be described in detail. The direct throttle movement controlis executed in accordance with the flow chart shown in FIG. 9.

Referring to FIG. 9, at first at step B101, a throttle valve openingθ_(THD) corresponding to the accelerator pedal treadled amount APS readin at step A103 of FIG. 8(i) is read out from a map #MAPS shown in FIG.19 using the accelerator pedal treadled amount APS as a parameter, andthen the sequence advances to step B102.

At step B102, it is judged whether or not the flag I₁₁ mentionedhereinabove is equal to 1. In case I₁₁ =1 is judged, this indicates thatthe present control cycle falls on a timing at which opening or closingmovement of the throttle valve 31 should be performed. Accordingly, thesequence advances to step B103 at which opening or closing movement ofthe throttle valve 31 is performed, thereby completing the directthrottle movement control for the present control cycle. To thecontrary, in case I₁₁ =1 is not judged at step B102, this indicates thatthe present control cycle does not fall on a timing at which opening orclosing movement of the throttle valve 31 should be performed, andaccordingly, the direct throttle movement control for the presentcontrol cycle is completed without executing any further operation.

At step B103, a signal indicative of the throttle valve opening θ_(THD)read out at step B101 is delivered from the control section 25 to thethrottle valve pivoting section 26. The throttle valve pivoting section26 receives such signal at the actuator driving section 39 thereof anddelivers a driving signal to the throttle valve actuator 40 to pivot thethrottle valve 31 to a position at which the throttle valve openingpresents a value equal to θ_(THD). The throttle valve actuator 40 thuspivots the throttle valve 31 in response to such driving signal.

In this instance, the opening of the throttle valve 31 is detected bythe throttle valve opening detecting section 41, and results of thedetection are fed back to the actuator driving section 39. Thus, inresponse to the detection results, the actuator driving section 39continuously delivers a pivotally driving signal for the throttle valve31 for changing the throttle valve opening toward the value θ_(THD).When it is detected by the throttle valve opening detecting section 41that the throttle valve 31 has been pivoted to such position, theactuator driving section 39 stops delivery of the driving signal inresponse to such detection results. Consequently, the throttle valve 31is stopped at the position at which the throttle valve opening is equalto the value θ_(THD).

In the direct throttle movement control, the throttle valve openingθ_(THD) is determined only depending upon a treadled amount of theaccelerator pedal 27 as described above. Meanwhile, the throttle valveopening θ_(THD) and the accelerator pedal treadled amount APS have sucha proportional mutual relationship as shown in FIG. 19. Accordingly, thethrottle valve 31 is moved in accordance with movement of theaccelerator pedal 27 in such a condition that the accelerator pedal 27and the throttle valve 31 are mechanically coupled directly to eachother.

It is to be noted that, when the throttle valve 31 operates in thismanner to open or close the intake air path 30, the amount of air suckedinto the engine 13 is changed, and consequently, the amount of fuelsupply to the engine 13 which is determined by a fuel controlling device(not shown) in accordance with the amount of air detected by the intakeair amount detecting section 20 and also with a running condition of theengine 13 is changed. As a result, the amount of fuel actually injectedinto the intake air path 30 by a fuel injection device (not shown) ischanged, and consequently, the output power of the engine 13 is changed.

Subsequently, the non-direct throttle movement control at step A116 ofFIG. 8(i) will be described. The non-direct throttle movement control isexecuted in accordance with the flow chart shown in FIG. 10.

Referring to FIG. 10, at first at step C101, it is judged in accordancewith the contact information read in at step A103 of FIG. 8(i) whetheror not the contact of the brake switch 16 is in an on-state.

In this instance, in case the brake pedal 28 is in a treadled conditionin order to brake the vehicle, the contact of the brake switch 16 is inan on-state at step C101, and consequently the sequence advances to stepC102. To the contrary, if the brake pedal 28 is not in a treadledcondition, the contact of the brake switch 16 is not in an on-state, andconsequently the sequence advances to step C113. Accordingly, control ofdifferent contents is executed whether the brake pedal 28 is in atreadled condition or not.

At step C102 to which the sequence advances from step C101 at which itis judged that the brake pedal 28 is in a treadled condition, a flag I₇is reset to 0. The flag I₇ indicates, when it assume a value of 0, thatthe brake pedal 28 was in a treadled condition in the preceding controlcycle. Then at step C103, it is judged whether or not the value ofanother flag I₂ is equal to 1.

The flag I₂ indicates, when it assumes a value equal to 1, that, whenthe brake pedal 28 was treadled to decelerate the vehicle by means of abrake (not shown), a quick braking condition wherein the deceleration isgreater than a reference value has continued for an interval of timelonger than a reference interval of time. It is to be noted that thereference value and the reference interval of time are set in advance.

In case it is judged at step C103 that I₂ =1, the sequence advancesdirectly to step C112 which will be hereinafter described, but on thecontrary if it is not judged that I₂ =1, the sequence advances to stepC104.

At step C104 to which the sequence advances from step C103, it is judgedwhether or not the actual acceleration DVA₁₃₀ read in at step A103 ofFIG. 8(i) is smaller than a preset negative reference value K₂ (DVA₁₃₀<K₂). Since the actual acceleration DVA₁₃₀ presents a positive valuewhen the vehicle is being accelerated but presents a negative value whenthe vehicle is being decelerated, the judgment whether or not the actualdeceleration DVA₁₃₀ is smaller then the negative reference value K₂,that is, DVA₁₃₀ <K₂, is the same judgment whether or not thedeceleration of the vehicle is greater than a preset reference value.

When quick braking wherein the deceleration is high is being performedby the brake (not shown), it is judged at step C104 that DVA₁₃₀ <K₂, andthen the sequence advances to step C107. When quick braking is not beingperformed, it is not judged at step C104 that DVA₁₃₀ <K₂, and then thesequence advances to step C105.

At step C107, it is judged whether or not the value of a flag I₁ isequal to 1. The flag I₁ indicates, when it assumes a value equal to 1,that a timer TMA which measures a duration of a condition wherein theactual acceleration DVA₁₃₀ is smaller than the reference value K₂ (thatis, a condition wherein the deceleration is greater than the presetreference value) is counting time. If the timer TMA is already countingtime, it is judged at step C107 that I₁ =1, and then the sequenceadvances to step C110. To the contrary, in case the timer TMA is notcounting time, it is not judged that I₁ =1, and the sequence advances tostep C108 at which the value of the flag I₁ is changed to 1. Then atstep C109, counting of time by the timer TMA is started again, and thenthe sequence advances to step C110.

At step C110, it is judged whether or not the time t_(TMA) counted bythe timer TMA is greater than a preset reference time t_(K1) (t_(TMA)>t_(K1)). In case it is judged that t_(TMA) >t_(K1), the sequenceadvances to step C111 at which the value of the flag I₂ is changed to 1,whereafter the sequence advances to step C112. To the contrary, if it isnot judged at step C110 that t_(TMA) >t_(K1), the sequence directlyadvances to step C112. Consequently, the value of the flag I₂ is left as0.

On the other hand, in case it is not judged at step C104 that DVA₁₃₀ <K₂and consequently the sequence advances to step C105, the deceleration bythe brake (not shown) is lower than the reference value and accordinglycounting by the timer TMA is unnecessary. Thus, in preparation for sucha possible case wherein counting by the timer TMA becomes necessary, thevalue of the flag I₁ is changed to zero at step C105, and then at stepC106, the timer TMA is reset to stop counting of time and change thevalue of the count time t_(TMA) to zero, whereafter the sequenceadvances to step C112.

It is to be noted that, if the condition wherein the deceleration by thebrake (not shown) is higher than the reference value continues for aninterval of time longer than a reference interval of time by the controlat such steps C103 to C111 as described above, the value of the flag I₂is changed to 1, and once the value of the flag I₂ is set to 1, it willnot be changed any more even if the deceleration becomes lower than thereference value unless the value of the flag I₂ is changed to 0 at anystep other than the steps C103 to C111.

At step C112, a signal to designate a throttle valve opening of aminimum value corresponding to the idling position of the engine 13 isdelivered from the controlling section 25 to the throttle valve pivotingsection 26. The throttle valve pivoting section 26 receives the signaland causes the actuator driving section 39 thereof to deliver to thethrottle valve actuator 40 a driving signal to pivot the throttle valve31 to the throttle valve opening of the minimum value. The throttlevalve actuator 40 thus pivots the throttle valve 31 in accordance withthe driving signal thus received.

In this instance, the opening of the throttle valve 31 is detected bythe throttle valve opening detecting section 41, and results of suchdetection are fed back to the actuator driving section 39 to effectfeedback control. In short, the actuator driving section 39 continues,in response to results of the detection of the throttle valve opening,to deliver a driving signal necessary for pivotal motion of the throttlevalve 31 until it is confirmed that the throttle valve 31 has beenpivoted to a predetermined position. When it is detected by the throttlevalve opening detecting section 41 that the throttle valve 31 has beenpivoted to the predetermined position, delivery of the driving signalfrom the actuator driving section 39 is stopped, and consequently thethrottle valve 31 is stopped at a predetermined position so that abraking force is caused by engine brake.

As described so far, if the brake pedal 28 is treadled, then this isintended for deceleration of the vehicle, and accordingly, braking ofthe vehicle by engine brake is performed together with braking by thebrake (not shown) by maintaining the throttle valve 31 at the minimumopening corresponding to the engine idling position after the control atsteps C103 to C111 has been executed.

In case the brake pedal 28 is not treadled and consequently the sequenceadvances from step C101 to step C113, it is judged whether or not thevalue of the flag I₇ is equal to 1. While the flag I₇ indicates whetheror not the brake pedal 28 was treadled in the preceding control cycle asdescribed hereinabove, if the brake pedal 28 was not treadled, then theflag I₇ has a value equal to 1, but if the brake pedal 28 was treadled,the flag I₇ presents a value equal to 0. Accordingly, at step C113, itis judged whether or not the present control cycle is the first controlcycle after the brake pedal 28 has been released.

In case it is judged at step C113 that I₇ =1, that is, the presentcontrol cycle is not the first control cycle after the brake pedal 28has been released, the sequence advances to step C133. On the contraryif it is judged that I₇ ≠1, that is, the present control cycle is thefirst control cycle after the brake pedal 28 has been released, thesequence advances to step C114.

When the sequence advances from step C113 to step C114, various settingsand judgments are accomplished at steps C114 to C118.

At first at step C114, since the brake pedal 28 is not treadled anymore, there is no necessity of performing such counting of time by thetimer TMA as described above. Accordingly, in preparation for suchcounting in the following control cycle or cycles, the value of the flagI₁ is changed to zero.

Then at step C115, the value of the flag I₇ is changed to 1 because thebreak pedal 28 is not in a treadled condition any more, and then at stepC116, the timer TMA is reset to stop counting of time and change thevalue of the counted time t_(TMA) to 0 by a similar reason as at stepC114.

Subsequently at step C117, the value of a flag I₁₂ is changed to 0. Theflag I₁₂ indicates, when it assumes a value equal to 0, either thatopening or closing operation of the throttle valve 31 is not yetperformed in a control cycle (opening/closing timing cycle) which fallson a timing for opening or closing movement of the throttle valve 31which is first encountered after the automatic cruise mode control atstep C144 has been entered in any control cycle, or that, although suchopening or closing movement has been performed, opening or closingmovement of the throttle valve 31 is not yet performed in anopening/closing timing cycle which is first encountered after thedesignation of a running condition of the vehicle has been changed byoperation of the acceleration switch 45 or the changing over switch 46in the automatic cruise mode control.

Then at step C118, it is judged in accordance with the contactinformation read in at step A103 of FIG. 8(i) whether or not the contactof the accelerator switch 15 is in an on-state. In case the acceleratorpedal 27 is treadled and the contact of the accelerator switch 15 is inan off-state, the sequence advances to step C135 at which the value ofthe flag I₂ is changed to 0 and then at step C136, the value of a flagI₃ is changed to 1, whereafter the sequence advances to step C137. Theflag I₃ indicates, when it assumes a value equal to 0, that the throttlevalve 31 should be maintained at its minimum opening corresponding tothe idling position of the engine 13.

It is to be noted that, in case the value of the flag I₂ is set to 1 atstep C111, the value of the flag I₂ remains 1 until the control at stepC135 is executed subsequently. In other words, the value of the flag I₂is changed to 0 when the accelerator pedal 27 is treadled subsequently.

At step C137, an aimed acceleration is determined in accordance with theaccelerator pedal treadled amount APS detected by the treadled amountdetecting section 14, the changing rate DAPS of the treadled amountcalculated from the treadled amount APS by the control section 25 and avalue of the counter CAPCNG, and accelerator mode control is executed.In the accelerator mode control, the throttle valve 31 is pivoted tocontrol the output power of the engine 13 so that the vehicle may run atan aimed acceleration. The non-direct throttle movement control in thepresent control cycle is completed with completion of the acceleratormode control.

In case the sequence advances from step C118 to C119 because theaccelerator pedal 27 is not treadled and the contact of the acceleratorswitch 15 is in an on-state, a value DAPMXO is changed to 0. The valueDAPMXO represents a maximum value of the changing rate DAPS of theaccelerator pedal treadled amount APS when the treadled amount of theaccelerator pedal 27 increases.

Then at step C120, another value DAPMXS is changed to 0. The valueDAPMXS represents a minimum value of the changing rate DAPS when thetreadled amount of the accelerator pedal 27 decreases.

Further at step C121, the latest actual speed VA_(I) calculated in theinterrupt control at steps A123 to A128 of FIG. 8(iv) is read in.

Subsequently at step C122, the value of the actual speed VA_(I) read inat step C121 is substituted as a value of V_(OFF) which indicates anactual speed of the vehicle at a point of time directly after the brakepedal 28 has been released.

Then at step C123, it is judged in accordance with the contactinformation read in at step A103 of FIG. 8(i) whether or not theposition of the throttle switch 47 of the automatic cruise switch 18 is[f] in FIG. 6. It is to be noted that, in case the throttle switch 47 isat the position [f], if the brake pedal 28 is released after it has beentreadled to decelerate the vehicle, it is designated to maintain thethrottle valve 31 at the minimum opening corresponding to the engineidling position until the accelerator pedal 27 is treadled subsequently.

In case it is judged at step C123 that the position of the throttleswitch 47 is [f], the sequence advances to step C126 at which the valueof the flag I₃ is changed to 0 and then to step C112 at which thethrottle valve 31 is pivoted to the minimum opening corresponding to theengine idling position as described hereinabove.

To the contrary, in case it is judged at step C123 that the position ofthe throttle switch 47 is not [f], the sequence advances to step C124 atwhich it is judged whether or not the value V_(OFF) is smaller than apreset reference value K₁, that is, V_(OFF) <K₁.

In case V_(OFF) <K₁ is judged at step C124, the sequence advances tostep C125 at which it is judged whether or not the value of the flag I₂is equal to 1. If I₂ =0 is judged, the sequence advances to step C126 atwhich the value of the flag I₃ is changed to 0 and then to step C112 atwhich the throttle valve 31 is pivoted to the minimum opening positionas described hereinabove.

To the contrary, if V_(OFF) <K₁ is not judged at step C124 or if I₂ =1is not judged at step C125, the sequence advances to step C145.

Accordingly, in case a condition wherein the deceleration is smallerthan a reference value continues for an interval of time longer than areference interval of time in response to treadling of the brake pedal28 to perform braking of the vehicle and besides the speed of thevehicle when such braking is interrupted is smaller than a referencevalue, if the accelerator pedal 28 is not treadled any more, braking ofthe vehicle is effected preferentially so that, even after the brakepedal 28 has been released, the throttle valve 31 is held at the minimumopening position to effect braking by engine brake.

When deceleration by the brake is to be performed to stop the vehicle,for example, at a crossing, the brake pedal 28 is released once directlybefore stopping in order to moderate a shock upon stopping. In such aninstance, however, the throttle valve 31 is maintained at the minimumopening to automatically effect braking by engine brake as describedhereinabove.

If the sequence advances from step C124 or step C125 to step C145, thenthe value of a flag I₄ is changed to 0 whereafter the sequence advancesto step C127. It is to be noted that the flag I₄ indicates, when itassumes a value equal to 0, that constant speed running should bedesignated by the running condition designating section 3 of the controlsection 25.

At step 127, the value of the flag I₃ is changed to 1 because there isno necessity of maintaining the throttle valve 31 at the minimumopening. Then at step C128, the value of the flag I₈ is changed to 1,and then at step C129, the actual speed VA_(I) read in at step C121 issubstituted into the aimed speed VS for constant speed running.

Subsequently at step C130, an aimed torque TOM₁ necessary to maintainrunning of the vehicle at the aimed speed VS is calculated by theconstant speed running aimed torque calculating section 219 inaccordance with the following equation (1):

    TOM.sub.1 =[{(W·r/g)·ks+ki}·(DVS.sub.3 -DVS.sub.65)+T.sub.Q ·TEM]/T.sub.Q               (1)

It is to be noted that, in the equation (1) above, W is a weight of thevehicle detected by the car weight detecting section 19 and read in atstep A103 of FIG. 8(i), r is an effective radius of a tire of the leftfront wheel 33 or the right front wheel 34 which is stored in advance,and g is the gravitational acceleration.

Of those parameters, data of the weight W of the vehicle which isinputted at step A103 of FIG. 8(i) is not a fixed value but a valueobtained by measurement.

In short, the car weight detecting section 19 detects a weight of thevehicle continuously or in a predetermined cycle while the vehicle stopsand is running, and car weight data is set from such detection value bythe control section 25 in accordance with a flow, for example, shown inFIG. 8(vii).

Referring to FIG. 8(vii), it is first judged at step R101 whether or notthe speed Va of the vehicle is equal to 0, that is, whether or not thevehicle is in a stopping condition. If it is judged that the vehicle isin a stopping condition, the sequence advances to step R102 at which anewly detected car weight value WHGT1 during stopping is set in any caseas data WHGT of the car weight W. Accordingly, while the vehicle remainsin a stopping condition, each time a variation is detected in a detectedcar weight WHGT1, the data WHGT of the car weight W is updated.

On the other hand, in case it is judged at step R101 that the speed Vaof the vehicle is not equal to 0, that is, the vehicle is running, thesequence advances to step R103 at which it is judged whether the vehicleis in a braked condition. If the vehicle is being braked, the sequenceadvances to step R104 at which a newly detected car weight value WHGT2is set in any case as data WHGT of the car weight W. Accordingly, whenthe vehicle is running but in a braked condition, data WHGT of the carweight W is updated each time a variation in the detected car weightWHGT2 is detected.

If it is judged at step R103 that the vehicle is running without beingbraked, a last car weight value WHGT1 or WHGT2 updated already is usedas the car weight data WHGT.

It is to be noted that the "braked condition" at step R103 signifiesthat "no throttle control is being executed", and when the vehicle is inan ordinary running condition in which throttle control is executed, adisturbance such as vibrations during running will have an influence oncar weight data such that the stability of data will be deteriorated tomake throttle control unstable, and therefore, data of the weight W ofthe vehicle is not updated in such case. However, when throttle controlis not executed, there is no inconvenience even if data of the weight Wof the vehicle is updated continually.

It is to be noted that measurement of a car weight by the car weightdetecting section 19 during braking is calculated correcting aninclination of the car body.

Further, ks is a coefficient set in advance for conversion of any valueinto a value where the gear position used of the automatic transmission32 is the low gear position and has a predetermined value correspondingto a gear position of the automatic transmission 32 in use as detectedby the gear position detecting section 23 and read in at step A103.Meanwhile, ki is a correction amount for inertia of the engine 13 andthe automatic transmission 32 around a drive shaft of the vehicle.

Furthermore, T_(Q) is a torque ratio of the automatic transmission 32.The torque ratio T_(Q) (which is sometimes represented briefly as therein) is determined in accordance with a map #MTRATQ (not shown) setin advance in accordance with characteristics of the automatictransmission 32 using a speed ratio e detected by the output rotationalspeed detecting section 22 as a parameter. It is to be noted that thespeed ratio e is obtained by the speed ratio calculating section 213 bydividing the output shaft rotation speed N_(D) of the torque converter(not shown) in the automatic transmission 32 read in at step A103 by theengine rotational speed N_(E) detected by the engine rotational speeddetecting section 21 and read in at step A103.

Further, DVS₃ is an aimed acceleration for making the speed of thevehicle equal to the aimed speed VS and maintaining the same. The aimedacceleration DVS₃ is determined by a map #MDVS3 set in advance as shownin FIG. 23 using a difference VA-VS of the actual speed VA from theaimed speed VS as a parameter. It is to be noted that, at step C130,since the aimed speed VS is an actual speed at a point of time directlyafter the break pedal 28 has been released as described hereinabove,determination of the aimed acceleration DVS₃ is effected on theassumption that the difference VS-VA is 0 in the equation (1) above.

Meanwhile, DVA₆₅ is an actual acceleration calculated in the interruptcontrol at steps A123 to A128 of FIG. 8(i) and read in at step A103 asdescribed hereinabove, and TEM is an actual torque of the output powerof the engine 13.

The actual torque TEM is determined in accordance with a map #TEMAP (notshown) set in advance in accordance with characteristics of the engine13, using, as parameters, the engine rotational speed N_(E) and a valueA_(E) /N_(E) which is obtained by dividing the intake air amount A_(E)detected by the intake air amount detecting section 20 and read in atstep A103 by the engine rotational speed N_(E). Here, however, theactual torque TEM is determined in the following manner in accordancewith characteristics of the automatic transmission 32 (torque converter207):

An absorbed torque Tti of the torque converter 207 is calculated inaccordance with an equation

    Tti=C·N.sub.E.sup.2                               (1-1)

where C is a torque capacity coefficient of the torque converter 207,and N_(E) is an engine rotational speed as described above.

It is to be noted that the torque capacity coefficient C depends uponcharacteristics of the torque converter 207 using the speed ratio ementioned hereinabove as a parameter. Here, the torque capacitycoefficient C is determined by the torque capacity coefficient settingsection 214 using a map #MTRATQC (not shown) which is provided inadvance using a speed ratio e as a parameter. Meanwhile, during normaldriving such as during acceleration wherein N_(E) >N_(D) stands, thespeed ratio e is equal to a value obtained by dividing an output shaftrotational speed N_(D) of the torque converter 207 by an enginerotational speed N_(E), that is, e=N_(D) /N_(E), but upon reversedriving (inertial running or the like) wherein N_(E) <N_(D) stands, thespeed ratio e is equal to a value obtained by dividing an enginerotational speed N_(E) by an output shaft rotational speed N_(D) of thetorque converter 207, that is, e=N_(E) /N_(D).

Meanwhile, since an output torque Tto of the torque converter 207corresponding to an actual torque TEM is a product of an absorbed torqueTti of the torque converter 207 and a torque ratio T_(Q) determinedusing the map #MTRATQ described above, a following equation is obtained:

    TEM=Tto=T.sub.Q ·Tti=T.sub.Q ·C·N.sub.E 2(1-2)

The actual torque TEM is thus calculated as such output torque Tto froma torque ratio T_(Q) and a torque capacity coefficient C of the torqueconverter 32 and a rotational speed N_(E) of the engine.

It is to be noted that, where a value of a reciprocal number (1/T_(Q))of a torque ratio T_(Q) determined using the map #MTRATQ is used as aparameter, there is another means wherein, using a torque ratio T_(Q)obtained from the map #MTRATQ, a reciprocal number of T_(Q) is found outby calculation each time 1/T_(Q) is to be used. However, in order toprevent a possible delay in control, another map #MTRATTQ (not shown)for 1/T_(Q) is prepared in advance in accordance with characteristics ofthe automatic transmission 32 using a speed ratio e as a parameter, anda value of 1/T_(Q) is found out using the map #MTRATTQ.

After the aimed torque TOM₁ is calculated at step C130 in this manner, athrottle valve opening θ_(TH1) is read out from a map #MTH (not shown)at subsequent step C131. The map #MTH is set in advance in accordancewith characteristics of the engine 13 using an aimed torque TOM and therotational speed N_(E) as parameters. The map #MTH is used fordetermination of a throttle valve opening θ_(TH) which is necessary tomake the output torque of the engine 13 equal to the aimed torque TOM.Accordingly, the value of a throttle valve opening θ_(TH1) to be readout from the map #MTH corresponds to the aimed torque TOM₁ calculated atstep C130 and also to the engine rotational speed N_(E) detected by theengine rotational speed detecting section 21 and read in at step A103.

At step C132, the throttle valve 31 is actuated in accordance with thethrottle valve opening θ_(TH1) read out from the map #MTH at step C131.In short, a signal indicative of the throttle valve opening θ_(TH1) isdelivered from the control section 25 to the throttle valve pivotingportion 26. The throttle valve pivoting section 26 thus receives thesignal at the actuator driving section 39 thereof and delivers a drivinga signal to the throttle valve actuator 40 to pivot the throttle valve31 to a position at which the throttle valve opening θ_(TH1) isprovided. In response to the driving signal, the throttle valve actuator40 pivots the throttle valve 31.

Also in this instance, adjustment of the opening of the throttle valve31 is effected by feedback control by way of the throttle valve openingdetecting section 41. After the throttle valve 31 is pivoted to apredetermined position, the actuator driving section 39 no more deliversa signal, and consequently the throttle valve 31 is stopped at thepredetermined position.

The intake air path 30 is opened or closed by such adjustment of thethrottle valve 31 to change the amount of air to be sucked into theengine 13 as described above. An amount of fuel to be supplied to theengine 13 is thus determined in accordance with results of suchdetection of the air amount by the fuel controlling device (not shown),and also the amount of fuel supply is changed. As a result, the outputpower of the engine 13 is adjusted so that a torque substantially equalto the aimed torque TOM₁ is produced from the engine 13.

The output torque of the engine 13 is substantially equal to a torquewhich is sufficient to maintain, as an aimed speed, the actual speed ofthe vehicle at a point of time directly after releasing of the brakepedal 28 as described hereinabove.

By the control at steps C129 to C132 described above, the throttle valve31 is temporarily pivoted, directly after releasing of the brake pedal28, to a position of a throttle valve opening which is forecast tomaintain the speed of the vehicle at a point of time directly afterreleasing of the brake pedal 28 even when the present control cycle isnot an opening/closing timing cycle determined by the reference timet_(K2) in order to make preparations for subsequent transition toconstant speed running at the aimed speed.

In case the sequence advanced from step C113 to step C114 to executesuch control as described above in the preceding control cycle and thebrake pedal 28 still remains in a released condition in the presentcontrol cycle, it is judged at step C113 that I₇ =1 because the value ofthe flag I₇ was changed to 1 at step C115 in the preceding controlcycle. The sequence thus advances to step C133 at which it is judged inaccordance with the contact information read in at step A103 whether ornot the contact of the accelerator switch 15 is in an on-state.

In case the accelerator pedal 27 is in a treadled condition, it isjudged at step C133 that the contact of the accelerator switch 15 is notin an on-state, and the sequence advances to step C134 at which thevalue of the flag I₁₂ is changed to 0 and then to step C135 at which thevalue of the flag I₂ is changed to 0. After then, the value of the flagI₃ is changed to 1 at step C136, and then the sequence advances to stepC137.

It is to be noted that, once the value of the flag I₂ is changed to 1 atstep C111, the value will not be changed until the control at step C135is completed subsequently as described hereinabove. Further, while thesequence advances to step C135 either from step C118 or from step C133via step C134, either case occurs when the accelerator pedal 27 istreadled to change the contact of the accelerator switch 15 to anoff-state. Accordingly, if the accelerator pedal 27 is treadled toaccelerate the vehicle again, then the value of the flag I₂ is changedto 0 at step C135.

Further, while the accelerator mode control is executed at step C137,such accelerator mode control is executed without fail if theaccelerator pedal 27 is treadled similarly as at step C136.

When the accelerator pedal 27 is not in a treadled condition, it isjudged at step C133 that the contact of the accelerator switch 15 is inan on-state, and the sequence thus advances to step C138. At step C138,the value of the maximum value DAPMXO is changed to 0, and then at stepC139, the value of the minimum value DAPMXS is changed to 0, whereafterit is judged at step C140 whether or not the value of the flag I₃ isequal to 1.

It is to be noted here that the accelerator switch 15 is in an on-stateonly when the accelerator pedal 27 is not treadled after decelerationperformed by the brake (not shown) has been completed by releasing thebrake pedal 28. This corresponds to a case wherein the control at stepsC113 to C132 described hereinabove was executed in the preceding controlcycle.

The flag I₃ indicates, when it assumes a value equal to 0, that thethrottle valve 31 should be kept at the minimum opening positioncorresponding to the engine idling position. Thus, in case I₃ =1 isjudged at step C140, the sequence advances to step C141, but on thecontrary if I₃ =1 is not judged, the sequence advances to step C112 tomove the throttle valve 31 to the minimum opening corresponding to theengine idling position.

It is to be noted that the value of the flag I₃ is changed to 0 when thesequence advances to step C126 as described hereinabove. Accordingly,when the throttle switch 47 is at the position [f] shown in FIG. 6 andwhen the condition wherein the deceleration is higher than the referencevalue continues for an interval of time longer than the referenceinterval of time upon deceleration by the brake (not shown) and thespeed of the vehicle upon completion of the deceleration is lower thanthe reference value, the throttle valve 31 is maintained at the minimumopening to effect braking by engine brake so long as the acceleratorpedal 27 and the brake pedal 28 are both in a released condition.

To the contrary, in case the sequence advances from step C140 to stepC141, it is judged at step C141 whether or not the value of the flag I₁₂is equal to 1, and in case it is judged that I₁₂ =1, the sequenceadvances to step C143, but on the contrary if it is not judged that I₁₂=1, the sequence advances to step C142.

The flag I₁₂ having a value equal to 0 indicates, as describedhereinabove, either that opening or closing operation of the throttlevalve 31 is not yet performed in a control cycle which falls on a timingfor opening or closing movement of the throttle valve 31 which is firstencountered after the automatic cruise mode control at step C144 hasbeen entered in any control cycle, or that, although such opening orclosing operation has been performed, opening or closing operation ofthe throttle valve 31 is not yet performed in a control cycle whichfalls on a timing for opening or closing of the throttle valve 31 whichis first encountered after the designation of a running condition of thevehicle has been changed by operation of the acceleration switch 45 orthe changing over switch 46 in the automatic cruise mode control.

Accordingly, in case the value of the flag I₁₂ is equal to 0, there isthe possibility that the opening of the throttle valve 31 may varysignificantly when the running condition of the vehicle is changed inresponse to operation of the acceleration switch 45 or the changing overswitch 46 upon or after transition to a running condition of the vehicleby the automatic cruise mode control.

Therefore, in order to assure more accurate opening or closing movementof the throttle valve 31 to a required opening to effect rapidtransition or change, a data is required which best follows a change inactual value to a point of time directly before such opening or closingmovement of the throttle valve 31 and has a value nearest to the actualvalue.

Thus, the sequence advances to step C142 at which the actualacceleration DVA₆₅ which has a value nearest to the actual accelerationof the vehicle and has a highest follow-up performance to such change inacceleration is adopted as a value of the actual acceleration DVA whichis to be used in the automatic cruise control.

To the contrary, in case the value of the flag I₁₂ is equal to 1, theopening of the throttle valve 31 is not changed by a great amountbecause opening or closing movement has been performed already upon suchtransition or change as described above. Accordingly, even if thefollow-up performance is lowered a little, the difference between theactual value and the measured data is small, and rather, stress shouldbe laid on the stability in control. Thus, the sequence advances to stepC143 at which the actual acceleration DVA₁₃₀ which is lower in follow-upperformance but is higher in stability is adopted as a value of theactual acceleration DVS.

After setting of a value of the acceleration DVA at step C142 or stepC143, the sequence advances to step C144 at which such automatic cruisemode control as hereinafter described is executed, thereby completingthe non-direct throttle movement control in the present control cycle.

By execution of the non-direct throttle movement control shown at stepsC101 to C144 of FIG. 10 in such a manner as described above, when thebrake pedal 28 is treadled to effect braking of the vehicle by means ofthe brake (not shown), the throttle valve 31 is held at the minimumopening corresponding to the engine idling position to effect braking byengine brake in addition to the braking by the brake. To the contrary,when the brake pedal 28 is released while the accelerator pedal 27 istreadled, the accelerator mode control which will be hereinafterdescribed is executed.

On the other hand, when the condition wherein the deceleration by thebrake pedal 28 is higher than the reference value continues for aninterval of time longer than the reference interval of time and thespeed of the vehicle directly after the brake pedal 28 is released islower than the reference value, although the brake pedal 28 has beenreleased, the throttle valve 31 is maintained at the minimum opening tocontinue braking by engine brake until the accelerator pedal 27 istreadled again.

When the deceleration is lower than the reference value or when thecondition wherein the deceleration is higher than the reference valuecontinues for an interval of time shorter than the reference interval oftime or when the speed of the vehicle after releasing of the brake pedal28 is higher than the reference value, the throttle valve 31 istemporarily pivoted to such a throttle valve opening at which thevehicle makes constant speed running wherein the speed of the vehicledirectly after releasing of the brake pedal 28 is maintained until theaccelerator pedal 27 is subsequently treadled. After then, the automaticcruise mode control is executed.

In the automatic cruise mode control, constant speed running of thevehicle is performed as hereinafter described until contact informationof the automatic cruise switch 18 exhibits some change after releasingof the brake pedal 28. In this instance, however, there is norelationship between a timing of such releasing of the brake pedal 28and a timing of opening or closing movement of the throttle valve 31,and the timing at which the brake pedal 28 is released may not alwayscoincide with the timing of opening or closing movement of the throttlevalve 31.

Therefore, directly after releasing of the brake pedal 28, the throttlevalve 31 is temporarily pivoted to a position thereof at which such athrottle valve opening as described above (throttle valve opening atwhich the vehicle can maintain constant speed running at the speeddirectly after releasing of the brake pedal 28) is provided, and thenthe automatic cruise mode control is executed in a throttle valveopening/closing timing cycle in the subsequent control cycle or cycles.

Where the speed of the vehicle is controlled in this manner, transitionto constant speed running proceeds with little variation in speed of thevehicle from a point of time directly after releasing of the brake pedal28.

Also when the accelerator pedal 27 is released after the acceleratormode control described below has been executed by releasing the brakepedal 28 and then treadling the accelerator pedal 27, such automaticcruise mode control is executed.

Subsequently, description will be given of details of the acceleratormode control which is executed at step C137 (FIG. 10) of the non-directthrottle movement control. The accelerator mode control is executed bythe control section 25 in accordance with the flow chart of steps D101to D126 shown in FIG. 11.

Referring to FIG. 11, at first at step D101, it is judged whether or nota map #MDVS6S has been used to find out an aimed acceleration DVS₆ inthe preceding control cycle. The map #MDVS6S is provided to find out anaimed acceleration DVS₆ using an accelerator pedal treadled amount APSas a parameter as shown in FIG. 20 and is used when the treadled amountof the accelerator pedal 27 is decreased. It is to be noted that theaccelerator pedal treadled amount APS is detected by the treadled amountdetecting section 14 and read in at step A102 of FIG. 8(i).

In case it is judged at step D101 that the map #MDVS6S was used in thepreceding control cycle, it is determined that the control for decreasein treadled amount has been executed in the preceding control cycle, andthe sequence advances to step D112. To the contrary, in case it isjudged at step D101 that the map #MDVS6S was not used in the precedingcontrol cycle, it is determined that the control for decrease intreadled amount was not executed in the preceding control cycle, thatis, the control for increase in treadled amount was executed in thepreceding control cycle, and the sequence advances to step D102.

At step D102, it is judged whether or not the changing rate DAPS of theaccelerator pedal treadled amount APS is smaller than a preset negativereference value K₆ (DAPS<K₆). It is to be noted that the changing rateDAPS of the accelerator pedal treadled amount APS is calculated in theinterrupt control at steps A121 to A122 of FIG. 8(iii) and read in atstep A103 of FIG. 8(i).

In case DAPS<K₆ is judged at step D102, it is determined that thetreadled amount of the accelerator pedal 27 is being decreased, and thesequence advances to step D103. But on the contrary if DAPS<K₆ is notjudged, it is determined that the treadled amount of the acceleratorpedal 27 is being increased, and the sequence advances to step D105.

In case the sequence advances to step D103, this means that the controlin the preceding control cycle was executed for increase in treadledamount and the control in the present control cycle is to be executed onthe contrary for decrease in treadled amount. Thus, the value of themaximum value DAPMXO of the changing rate DAPS during increase intreadled amount is changed to 0 at step D103, and then at subsequentstep D104, the value of the minimum value DAPMXS of the changing rateDAPS during decrease in treadled amount is changed to 0, whereafter thesequence advances to step D115. It is to be noted that the value DAPMXOnormally presents a value greater than 0 because it is a value duringincrease in treadled amount of the accelerator pedal 27, and on thecontrary, the value DAPMXS always presents a value smaller than 0because it is a value during decrease in treadled amount of theaccelerator pedal 27.

To the contrary, in case the sequence advances from step D101 to stepD112, it is judged at step D112 whether or not the changing rate DAPS isgreater than a preset positive reference value K₇ (DAPS>K₇). In caseDAPS>K₇ is judged at step D112, it is determined that the treadledamount of the accelerator pedal 27 is being increased, and the sequenceadvances to step D113. But on the contrary if DAPS>K₇ is not judged atstep D112, it is determined that the treadled amount of the acceleratorpedal 27 is being decreased, and the sequence advances to step D115.

When the sequence advances to step D113, the control in the precedingcontrol cycle was executed for decrease in treadled amount and thecontrol in the present control cycle is to be executed on the contraryfor increase in treadled amount. Thus, the value of DAPMXO is changed to0 at step D113, and then the value of DAPMXS is changed to 0 atsubsequent step D114, whereafter the sequence advances to step D105.

Accordingly, in case it is judged that the treadled amount of theaccelerator pedal 27 is being increased (being increased continuously),control of steps D122 to D130 and then steps D123 to D126 is executedafter execution of steps D105 to D111. On the contrary, in case it isjudged that the treadled amount of the accelerator pedal 27 is beingdecreased (being decreased continuously), control of steps D122 to D126is executed after execution of steps D115 to D121.

In case the sequence advances to step D105, an aimed acceleration DVS₆corresponding to the accelerator pedal treadled amount APS detected bythe treadled amount detecting section 14 and read in at step A103 ofFIG. 8(i) is read cut from a map #MDVS6O. The map #MDVS6O is provided tofind out an aimed acceleration DVS₆ during increase in treadled amountof the accelerator pedal 27 using the accelerator pedal treadled amountAPS as parameter. The values of APS and DVS₆ have such a relationship asillustrated in the map #MDVS6O of FIG. 20.

At subsequent step D106, the value of DAPMXO stored in the precedingcontrol cycle is compared with the value of DAPS of the present controlcycle. Then, if it is judged that DAPMXO<DAPS, DAPS is substituted intothe DAPMXO as a new value at step C107, and then the sequence advancesto step D108. To the contrary, if DAPMXO<DAPS is not judged at stepD106, DAPMXO stored in the preceding control cycle remains stored as itis, and then the sequence advances to step D108.

At step D108, an aimed acceleration DVS₇ corresponding to the valueDAPMXO is read out from a map #MDVS7O in such a manner as describedabove. The map #MDVS7O is provided to find out an aimed accelerationDVS₇ during increase in treadled amount of the accelerator pedal 27using DAPMXO as a parameter. The values of DAPMXO and DVS₇ have such arelationship as illustrated in the map #MDVS7O of FIG. 21.

As apparently seen from the relationship illustrated in the map #MDVS7Oof FIG. 21, the value of the aimed acceleration DVS₇ increases as theincrease in treadled amount of the accelerator pedal 27 occurs at a highratio in the control of steps D106 to D108. Since, however, the value ofthe aimed acceleration DVS₇ becomes fixed if the value DAPMXO exceeds acertain level, such excessively rapid acceleration as will causedeterioration in safety is inhibited.

In particular, at subsequent step D109, it is judged whether or not thechanging rate DAPS of the accelerator pedal treadled amount APS ishigher than a preset reference value K₈ (DAPS>K₈). If DAPS>K₈ is judged,then it is determined that the change in treadled amount of theaccelerator pedal 27 during increase is excessively great, and thesequence thus advances to step D110. To the contrary, if DAPS>K₈ is notjudged, it is determined that the change is not excessively great, andthe sequence thus advances to step D111. In case the sequence advancesfrom step D109 to step D110, the value of the counter CAPCNG is changedto 1, and then the sequence advances to step D111.

At step D111, an aimed acceleration DVS₈ corresponding to the value ofthe counter CAPCNG is read out from a map #MDVS8O. The map #MDVS8O isprovided to find out an aimed acceleration DVS₈ during increase intreadled amount of the accelerator pedal 27 using the value of thecounter CAPCNG as a parameter. The value of the counter CAPCNG and thevalue of the aimed acceleration DVS₈ have such a relationship asillustrated in the map #MDVS8O of FIG. 22.

The value of the counter CAPCNG used at step D111 is set in theinterrupt routine of steps A118 to A120 of FIG. 8(i) as describedhereinabove and remains 0 so far as any value other than 0 issubstituted into the counter CAPCNG. When the value of the counterCAPCNG is equal to 0, an aimed acceleration DVS₈ which is read out fromthe map #MDVS8O at step D111 also presents a value 0 as apparently seenfrom the map MDVS8O of FIG. 22. To the contrary, when the changing rateDAPS is greater than the reference value K₈, the value of the counterCAPCNG is changed to 1 at step D110 as described above. Accordingly, solong as the changing rate DAPS is greater than the reference value K₈,the value of the counter CAPCNG remains 1. Accordingly, in thisinstance, an aimed acceleration DVS₈ read out from the map #MDVS8O atstep D111 presents a maximum value in the map #MDVS8O as apparently seenfrom the map #MDVS8O shown in FIG. 22.

When the sequence comes to step D109 again past step D102 in thesubsequent next control cycle after the value of the counter CAPCNG ischanged to 1 at step D110, now DAPS>K₈ is not judged at step D109because the increase in treadled amount of the accelerator pedal 27 waseither moderated or interrupted. Consequently, the sequence now advancesto step D111 bypassing step D110. At step D111, the value of the counterDAPCNG becomes a value which is determined in the interrupt control ofsteps A118 to A120 of FIG. 8(ii). In the interrupt routine, the value ofthe counter CAPCNG is incremented by 1 as a new value of the counterCAPCNG.

At subsequent step A119, it is judged whether or not the value of thecounter CAPCNG is equal to 1. Here, if the value of the counter CAPCNGis changed to 1 at step D110 as described hereinabove, then the value ofthe counter CAPCNG is updated to 2 at step A118. Accordingly, thesequence bypasses step A120 depending upon such judgement at step A119,and the value of the counter CAPCNG upon completion of the interruptcontrol for the present time is 2.

Also in the following control cycles, the control at step D109 isexecuted, and accordingly, while the condition wherein DAPS>K₈ is notsatisfied continues, the value of the counter CAPCNG is incremented by 1in each such interrupt control as described above.

In case the sequence advances to step D109 via steps D102 to D105,judgment at step D102 has been such that the relationship between thechanging rate DAPS and the reference value K₆ is not DAPS<K₆ butDAPS≧K₆. Accordingly, the sequence advances from step D109 directly tostep D111 when the changing rate DAPS has a value defined by K₆≦DAPS≧K₈. As described hereinabove, the reference value K₆ has anegative value while the reference value K₈ has a positive value.Accordingly, if the treadled amount of the accelerator pedal 27 is heldconstant, then the value of the counter CAPCNG is increased one by oneas described above.

In this instance, the aimed acceleration DVS₈ read out from the mapMDVS8O at step D111 decreases in value as the value of the counterCAPCNG increases and finally decreases to 0 as apparently seen from themap #MDVS8O in FIG. 22. Accordingly, if the treadled amount of theaccelerator pedal 27 is held substantially constant after it has beenincreased, then the value of the aimed acceleration DVS₈ having apositive value gradually approaches 0 as time passes.

To the contrary, in case the sequence advances to step D115 either fromstep D104 or from step D112, an aimed acceleration DVS₆ corresponding tothe accelerator pedal treadled amount APS detected by the treadledamount detecting section 14 and read in at step A103 of FIG. 8(i) isread out at step D115 from a map #MDVS6S. It is to be noted that the map#MDVS6S is provided to find out an aimed acceleration DVS₆ duringreduction in treadled amount of the accelerator pedal 27 using theaccelerator pedal treadled amount APS as a parameter. The values of APSand DVS₆ have such a relationship as seen in #MDVS6S shown in FIG. 20.

At subsequent step D116, the value DAPMXS stored in the precedingcontrol cycle is compared with the value DAPS in the present controlcycle. In case it is judged that DAPMXS>DAPS, the value of DAPS issubstituted, at step D117, into DAPMXS as a new value of DAPMXS, andthen the sequence advances to step D118. To the contrary, if it is notjudged that DAPMXS>DAPS, the value DAPMXS stored in the precedingcontrol cycle remains stored as it is, and the sequence advances to stepD118.

At step D118, an aimed acceleration DVS₇ corresponding to the DAPMXSdetermined in such a manner as described above is read out from a map#MDVS7S. The map #MDVS7S is provided to find out an aimed accelerationDVS₇ during reduction in treadled amount of the accelerator pedal 27using DAPMXS as a parameter. The values of DAPMXS and DVS₇ have such arelationship as illustrated in the map #MDVS7S shown in FIG. 21. It isto be noted that, since the value of DAPMXS is a changing rate intreadled amount when the treadled amount of the accelerator pedal 27 isbeing decreased, it has a value equal to 0 or a negative value asdescribed hereinabove, and accordingly the aimed acceleration DVS₇ has anegative value as illustrated in the map #MDVS7S shown in FIG. 21.Accordingly, the absolute value of the aimed acceleration DVS₇ is adeceleration.

In this manner, in the control of steps D116 to D118, the aimedacceleration DVS₇ decreases in negative value as the rate in reductionin treadled amount of the accelerator pedal 27 increases as apparentlyseen from the relationship shown in FIG. 21.

At subsequent step D119, it is judged whether or not the changing rateDAPS of the accelerator pedal treadled amount APS is smaller than apresent negative reference value K₉ (DAPS<K₉). In case DAPS<K₉ isjudged, it is determined that the change in reduction in treadled amountof the accelerator pedal 27 is greater, and the sequence advances tostep D120. To the contrary, if DAPS<K₉ is not judged at step D119, it isdetermined that the change is smaller, and the sequence advances to stepD121. In case the sequence advances from step D119 to step D120, thevalue of the counter CAPCNG is changed to 1, and then the sequenceadvances to step D121.

At step D121, an aimed acceleration DVS₈ corresponding to the value ofthe counter CAPCNG is read out from a map #MDVS8S. The map #MDVS8S isprovided to find out an aimed acceleration DVS₈ during reduction intreadled amount of the accelerator pedal 27 using the value of thecounter CAPCNG as a parameter. The value of the counter CAPCNG and thevalue of DVS₈ have such a relationship as illustrated in the map #MDVS8Sshown in FIG. 22. It is to be noted that, since the aimed accelerationDVS₈ assumes a value equal to 0 or a negative value as seen in the map#MDVS8S of FIG. 22, it indicates a deceleration.

The value of the counter CAPCNG used at step D121 is set in theinterrupt control of steps A118 to A120 of FIG. 8(ii) and is normallyequal to 0 unless any value other than 0 is substituted into the counterCAPCNG. Then, when the value of the counter CAPCNG is equal to 0, theaimed acceleration DVS₈ read out from the map #MDVS8S at step D121 alsoassumes a value equal to 0 as apparently seen from the map #MDVS8S shownin FIG. 22. To the contrary, when the changing rate DAPS is smaller thanthe reference value K₉, the value of the counter CAPCNG is changed to 0at step D120 as described hereinabove. Accordingly, while the changingrate DAPS remains smaller than the reference value K₉, the counterCAPCNG always has a value equal to 1, and in this instance, the aimedacceleration DVS₈ read out from the map #MDVS8S at step D121 has thesmallest negative value in the map #MDVS8S as apparently seen from themap #MDVS8S shown in FIG. 22 and accordingly presents a maximumdeceleration.

For example, if the value of the counter CAPCNG is changed to 1 at stepD120 and then it is judged at step D119 to which the sequence advancesagain via step D112 in the subsequent next control cycle that DAPS<K₉ isnot satisfied because reduction in treadled amount of the acceleratorpedal 27 has been moderated or interrupted, the sequence advances fromstep D119 to step D121. In this instance, since step D120 is bypassed,the value of the counter CAPCNG is a value determined in the interruptcontrol of steps A118 to A120 of FIG. 8(ii). In the interrupt control,the value of the counter CAPCNG added by 1 is designated as a new valueof the counter CAPCNG at step A118.

At subsequent step A119, it is judged whether or not the value of thecounter CAPCNG is equal to 1. However, since the value of the counterCAPCNG is updated to 2 at step D120 as described above, the sequencebypasses step A120 depending upon such judgment at step A119.Consequently, the value of the counter CAPCNG at a point of time whenthe present interrupt control is completed is equal to 2. Also in thefollowing control cycle or cycles, the control at step D119 is executed.Thus, so long as the condition wherein DAPS<K₉ is not satisfiedcontinues, the value of the counter CAPCNG is increased one by one ineach such interrupt control as described above.

In case the sequence advances from step D112 to step D119 via step D115,the judgment at step D112 has revealed that the changing rate DAPS andthe reference value K₇ do not have a relationship of DAPS>K₇ but have arelationship of DAPS≦K₇. Accordingly, the sequence advances from stepD119 directly to step D121 when the changing rate DAPS has a valuedefined by K₉ ≦DAPS≦K₇. Further, since the reference value K₇ has apositive value while the reference value K₉ has a negative value asdescribed hereinabove, if the treadled amount of the accelerator pedal27 is kept constant, then the value of the counter CAPCNG is increasedone by one as described hereinabove.

In this instance, the aimed acceleration DVS₈ read out from the map#MDVS8S at step D121 increases as the value of the counter CAPCNGincreases and finally reaches 0 as apparently seen from the map #MDVS8Sshown in FIG. 22. Accordingly, if the treadled amount of the acceleratorpedal 27 is reduced and then the treadled amount is kept substantiallyfixed, then the value of the aimed acceleration DVS₈ having a negativevalue gradually approaches 0 as time passes.

In case the sequence advances from step D111 to step D122, a sum totalof the aimed accelerations DVS₈, DVS₇ and DVS₈ found out in the controlof steps D105 to D111 is calculated as a general aimed accelerationDVS_(AP) for the accelerator mode control.

Then at subsequent step D127, it is judged whether or not the aimedacceleration DVS_(AP) based on treadling of the accelerator pedal 27 isgreater than an aimed acceleration DVS_(AC) designated by means of theautomatic cruise switch 18. It is to be noted that, while suchdesignation of an aimed acceleration DVS_(AC) by the automatic cruiseswitch 18 is hereinafter described, in case no aimed accelerationDVS_(AC) is designated by the automatic cruise switch 18 or in case suchdesignation of an aimed acceleration is cancelled, the value of theaimed acceleration DVS_(AC) is equal to zero then.

If the aimed acceleration DVS_(AP) is greater than the aimedacceleration DVS_(AC), then the sequence advances to step D129 at whichthe aimed acceleration DVS_(AP) based on treadling of the acceleratorpedal 27 is adopted as an aimed acceleration DVS. Then, at subsequentstep D130, the value of the aimed acceleration DVS_(AC) is changed tozero, whereafter the sequence advances to step D123.

On the contrary, if the aimed acceleration DVS_(AP) is not greater thanthe aimed acceleration DVS_(AC), then the sequence advances to step D128at which the aimed acceleration DVS_(AC) designated by the automaticcruise switch 18 is adopted as an aimed acceleration DVS, whereafter thesequence advances to step D123.

On the other hand, in case the sequence advances from step D121 to stepD131, a sum total of the aimed accelerations DVS₆, DVS₇ and DVS₈ foundout in the control of steps D115 to D121 is calculated as a generalaimed acceleration DVS_(AP) for the accelerator mode control.

Then, at subsequent step D132, the value of the aimed accelerationDVS_(AC) designated by the automatic cruise switch 18 is changed tozero, and then the sequence advances to step D133 at which the aimedacceleration DVS_(AP) based on treadling of the accelerator pedal 27 isadopted as an aimed acceleration DVS, whereafter the sequence advancesto step D123.

The reason will be described subsequently why, upon treadling of theaccelerator pedal 27, the aimed acceleration DVS_(AC) designated by theautomatic cruise switch 18 is adopted as an aimed speed of the vehicleuntil after the aimed acceleration DVS_(AP) based on treadling of theaccelerator pedal 27 becomes greater than the aimed accelerationDVS_(AC) designated by the automatic cruise switch 18.

In short, while the treadling amount or the treadling speed of theaccelerator pedal 27 remains low, the values of the aimed accelerationsDVS₆, DVS₇ and DVS₈ which are components of the aimed accelerationDVS_(AP) based on treadling of the accelerator pedal 27 remain also low,and hence the value of the aimed acceleration DVS_(AP) which is a sumtotal of the aimed accelerations DVS₆, DVS₇ and DVS₈ also remains low.Since the treadling amount and the treadling speed of the acceleratorpedal 27 are low at an initial stage of treadling of the acceleratorpedal 27, the value of the aimed acceleration DVS_(AP) is low then, andthe value of the aimed acceleration DVS_(AP) is sometimes smaller thanthe aimed acceleration DVS_(AC) designated by the automatic cruiseswitch 18.

Accordingly, if the accelerator pedal 27 is treadled down during controlof running of the vehicle in accordance with the aimed accelerationDVS_(AC) (during automatic cruise control) to change the control of thevehicle from automatic cruise control to accelerator mode control, thereis the possibility that the aimed acceleration may temporarily drop atan initial stage after such change. Since a change to accelerator modecontrol takes place normally when it is desired to obtain anacceleration higher than a current acceleration, even a temporary dropof the aimed acceleration is not desirable for rapid acceleration or forsmooth acceleration.

Accordingly, during such a period of time, the aimed accelerationDVS_(AC) having a greater value is adopted.

It is to be noted that characteristics of the aimed accelerations DVS₆,DVS₇ and DVS₈ will be hereinafter described.

Subsequently at step D123, an aimed torque TOM_(A) necessary to attainthe aimed acceleration DVS as an actual acceleration of the vehicle iscalculated in the following equation (2):

    TOM.sub.A =[{(W·r/g)·ks+ki}·DVS+R'·r]/T.sub.Q(2)

It is to be noted that W, r, g, ks, ki and T_(Q) in the equation (2)above are same as those used in the equation (1) given hereinabove fordescription of the non-direct throttle movement control, and R' is arunning resistance to running of the vehicle calculated in accordancewith the following equation (3):

    R'=μr·W+μair·A·VA.sub.2   (3)

It is to be noted that, in the equation (3) above, μr is a coefficientof rolling resistance of the vehicle, W is a car weight which is thesame as that used in the equation (2) above, μair is a coefficient ofair resistance of the vehicle, A is a frontal projected area of thevehicle, and VA is an actual speed of the vehicle calculated in theinterrupt control of steps A123 to A128 of FIG. 8(iv) and read in atstep A103 of FIG. 8(i).

At step D124 to which the sequence advances from step D123, a throttlevalve opening θ_(THA) corresponding to the aimed torque TOM_(A)calculated at step D123 and the rotational speed N_(E) of the engine 13detected by the engine rotational speed detecting section 21 and read inat step A103 of FIG. 8(i) is read out from the map #MTH. The map #MTH isthe same map as that used at step C131 of FIG. 10 for the non-directthrottle movement control described hereinabove.

At subsequent step D125, it is judged whether or not the flag I₁₁ isequal to 1. As described hereinabove, the flag I₁₁ indicates, when itassumes a value equal to 1, that the present control cycle is a controlcycle in which opening or closing movement of the throttle valve 31should be performed.

Since here the present control cycle is a control cycle in which suchopening or closing movement should be performed when the flag I₁₁ has avalue equal to 1, the sequence advances to step D126. On the contrary,if the value of the flag I₁₁ is not equal to 1, the present controlcycle is not a control cycle in which such opening or closing movementis to be performed, and accordingly the sequence bypasses step D126,thereby completing the accelerator mode control in the present controlcycle.

At step D126, a signal indicative of the throttle valve opening θ_(THA)read out at step D124 is delivered from the control section 25 to thethrottle valve pivoting section 26. The throttle valve pivoting section26 receives such signal at the actuator driving section 39 thereof anddelivers a required driving signal (to pivot the throttle valve 31 to aposition at which the throttle valve opening θ_(THA) is provided) to thethrottle valve actuator 40. The throttle valve actuator 40 thus pivotsthe throttle valve 31 in response to the driving signal received.

In this instance, the opening of the throttle valve 31 is detected bythe throttle valve opening detecting section 41, and results of thedetection are fed to the actuator driving section 39 to effect feedbackcontrol.

After the throttle valve 31 is pivoted to a predetermined position, theactuator driving section 39 no more delivers the driving signal, andconsequently, the throttle valve 31 is stopped at the predeterminedposition, thereby completing the accelerator mode control in the presentcontrol cycle.

By opening or closing of the intake air path 30 by the throttle valve 31in this manner, the amount of air and the amount of fuel sucked into theengine 13 are changed to adjust the output power of the engine 13 asdescribed above. Consequently, the vehicle is accelerated at anacceleration substantially equal to the aimed acceleration DVS.

As described so far, the accelerator mode control involves determinationof an aimed acceleration in accordance with a treadled amount of theaccelerator pedal 27, a changing rate of the treadled amount and thedirection of such change of the treadled amount as well as opening orclosing movement of the throttle valve 31 in accordance with the aimedacceleration thus determined to control the engine 13.

In particular, when the treadled amount APS of the accelerator pedal 27is increased, the values of the three aimed accelerations of DVS₆, DVS₇and DVS₈ from which the aimed acceleration DVS is to be calculatedexhibit the following variations.

At first, the value of DVS₆ increases as the treadled amount APSincreases because the value of DVS₆ is determined in accordance withsuch a relationship to the value of the treadled amount APS asillustrated in the map #MDVS6O of FIG. 20. Particularly, the faster theincrease of the treadled amount APS proceeds, the greater the rate ofincrease of the value of DVS₆.

Meanwhile, the value of DVS₇ presents a greater value as the increase ofthe treadled amount APS proceeds at a higher speed because the value ofDVS₇ is determined in accordance with such a relationship to the maximumvalue DAPMXO of the changing rate in treadled amount while the increaseof the treadled amount APS continues as illustrated in the map #MDVS7Oof FIG. 21.

On the other hand, because the value of DVS₈ is determined in accordancewith such a relationship to the value of the counter CAPCNG asillustrated in the map #MDVS8O of FIG. 22, when the increase of thetreadled amount APS proceeds at a rate higher than the reference level,the counter CAPCNG presents a value equal to 1, and the value of DVS₈presents a maximum value.

Since the aimed accelerations DVS₆, DVS₇ and DVS₈ vary in such mannersas described above, the faster the increase in treadled amount of theaccelerator pedal proceeds, the quicker the vehicle makes anacceleration.

To the contrary, in case the increase in treadled amount is stopped andthe treadled amount of the accelerator pedal 27 is kept at a fixedvalue, the aimed accelerations DVS₆, DVS₇ and DVS₈ present the followingvariations.

The value of DVS₆ presents a fixed value because it is determined inaccordance with such a relationship to the treadled amount APS asillustrated in the map #MDVS6O of FIG. 20.

Meanwhile, the value of DVS₇ also remains constant because a value whichhas been determined in accordance with such a relationship asillustrated in the map #MDVS7O of FIG. 21 in a similar manner to thatdescribed above upon increase of the treadled amount before the treadledamount APS is kept constant is maintained as it is.

On the other hand, the value of DVS₈ is reduced gradually as time passesand finally reduced to 0 as illustrated in the map #MDVS8O of FIG. 22because the value of the counter CAPCNG increases in accordance with atime elapsed after the increasing rate of the treadled amount APS hasreduced to a value lower than the reference value.

Accordingly, in case the increase in treadled amount is stopped and thetreadled amount of the accelerator pedal 27 is kept constant, the aimedacceleration DVS will gradually approach a fixed value.

In short, if the treadled amount APS of the accelerator pedal 27 isincreased to a suitable level, then the acceleration varies smoothlyfrom a quickly accelerating condition to a moderately acceleratingcondition.

To the contrary, if the treadled amount APS of the accelerator pedal 27is decreased, then the values of the aimed accelerations DVS₆, DVS₇ andDVS₈ vary in the following manners.

The value of DVS₆ is determined in accordance with such a relationshipto the treadled amount APS as illustrated in the map #MDVS6S of FIG. 20.Accordingly, the value of DVS₆ decreases as the treadled amount APSdecreases. The rate of such reduction of DVS₆ increases as the speed ofthe reduction of the treadled amount APS increases.

Meanwhile, the value of DVS₇ is determined in accordance with such arelationship to the minimum value DAPMXS of the changing rate of thetreadled amount (that is, the maximum value of the decreasing ratio)while the decrease of the treadled amount APS continues as illustratedin the map #MDVS7S of FIG. 21. Accordingly, the faster the decrease ofthe treadled amount APS proceeds, the smaller the value of DVS₇(negative value having a small absolute value).

On the other hand, the value of DVS₈ presents a minimum value (negativevalue having a maximum absolute value) as illustrated in the map #MDVS8Sof FIG. 22 when the decrease of the treadled amount APS proceeds at aspeed higher than the reference value so that the value of the counterCAPCNG is changed to 1.

Accordingly, the faster the decrease of the treadled amount APS of theaccelerator pedal 27, the earlier the acceleration of the vehicledecreases, and finally the vehicle is brought into a deceleratedcondition.

It is to be noted that the value of DVS₆ while the treadled amount isbeing increased is greater than the value of DVS₆ for a same treadledamount while the treadled amount is being decreased as seen from themaps #MDVS6O and #MDVS6S of FIG. 20.

Accordingly, even if the treadled amount is equal, quicker accelerationoccurs when the treadled amount is being increased than when thetreadled amount is being decreased.

Further, if the treadled amount is further decreased after the value ofDVS₆ has been decreased to 0, the value of DVS₆ becomes negative, asseen from the map #MDVS6S of FIG. 20. Consequently, also the aimedacceleration DVS calculated from the aimed accelerations DVS₆, DVS₇ andDVS₈ become negative, and as a result, the vehicle is decelerated inaccordance with the negative aimed acceleration.

To the contrary, in case the decrease of the treadled amount APS isstopped and then the treadled amount of the accelerator pedal 27 is keptconstant, the aimed accelerations present the following variations.

The value of DVS₆ exhibits a fixed value because it is determined inaccordance with such a relationship to the treadled amount APS asillustrated in the map #MDVS6S of FIG. 20.

Meanwhile, the value of DVS₇ presents a fixed value because a valuewhich has been determined in accordance with such a relationship to theminimum value DAPMXS of the changing rate of the treadled amount (thatis, maximum value of the decreasing ratio) upon decrease of the treadledamount before the treadled amount APS is kept constant as illustrated inthe map #MDVS7S of FIG. 21 is maintained as it is.

On the other hand, the value of DVS₈ increases gradually as time passesand finally becomes equal to 0 as illustrated in the map #MDVS8S of FIG.22 because the value of the counter CAPCNG increases in accordance witha time elapsed after a point of time at which the decelerating rate ofthe treadling amount APS becomes lower than the reference value.

When the treadled amount of the accelerator pedal 27 is decreased inthis manner, the acceleration is decreased smoothly from theacceleration decreasing condition or the decelerating condition andtransition to an accelerated condition at a fixed acceleration takesplace.

The automatic cruise mode control at step C144 of FIG. 10 executed inthe non-direct throttle movement control proceeds in accordance with theflow chart of steps E101 to E133 of FIG. 12.

The automatic cruise mode control is executed when neither of theaccelerator pedal 27 and the brake pedal 28 is treadled in thenon-direct throttle movement control described hereinabove.

Referring to FIG. 12, it is judged at first at step E101 whether or notthe contact of the accelerator switch 15 was in an on-state in thepreceding control cycle without the accelerator pedal 27 being treadled.In case the present cycle is a first cycle after the accelerator pedal27 has been released and the contact of the accelerator switch 15 hasbeen brought into an on-state, the sequence advances to step E102depending upon such judgment at step E101. On the contrary, in case theaccelerator pedal 27 was released and the contact of the acceleratorswitch 15 was already in an on-state already in the preceding controlcycle, the sequence advances to step E110 depending upon such judgmentat step E101.

Accordingly, the control in a first control cycle after the acceleratorpedal 27 is treadled to effect acceleration of the vehicle and is thenreleased is different from the control in control cycles following thefirst control cycle or in control cycles after the automatic cruise modecontrol is entered by releasing the brake pedal 28 while the acceleratorpedal 27 is not treadled.

At step E102 to which the sequence advances in a first control cycleafter the accelerator pedal 27 has been released, the value of a flag I₄is changed to 0, and then the sequence advances to step E103. The flagI₄ indicates, when it assumes a value equal to 0, that constant speedrunning should be designated by the running condition designatingsection 3 of the control section 25.

At step E103, the value of a flag I₆ is changed to 0, and then thesequence advances to step E104. The flag I₆ indicates, when it assumes avalue equal to 1, that the present control cycle is a first cycle afterthe contact of the changing over switch 46 has been brought into anon-state.

At step E104, the latest actual speed VA_(I) calculated in the interruptcontrol at steps A123 to A128 of FIG. 8(iv) is read in as an actualspeed of the vehicle directly after releasing of the accelerator pedal27, and then at step E105, the actual speed VA_(I) is substituted intothe aimed speed VS.

Then at step E106, the value of a flag I₈ is changed to 0. The flag I₈indicates, when it assumes a value equal to 0, that the speed of thevehicle is maintained substantially constant by the automatic cruisemode control.

Subsequently at step E107, an aimed torque TOM₃ of the engine 13necessary to maintain the speed of the vehicle at the aimed speed VS iscalculated in the following equation (4), and then the sequence advancesto step E108.

    TOM.sub.3 =[{(W·r/g)·ks+ki}·(DVS.sub.3 -DVS.sub.65)+T.sub.Q ·TEM]/T.sub.Q               (4)

It is to be noted that the equation (4) above is substantially the sameas the equation (1) used at step C130 in the flow chart of FIG. 10.

At step E108, a throttle valve opening θ_(TH3) corresponding to theaimed torque TOM₃ calculated at step E107 and the engine rotationalspeed N_(E) detected by the engine rotational speed detecting section 18and read in at step A103 of FIG. 8(i) is read out from the map #MTHdescribed hereinabove.

Subsequently at step E109, a signal indicative of the throttle valveopening θ_(TH3) is delivered from the control section 25 to the actuatordriving section 39 of the throttle valve pivoting section 26.Consequently, a required driving signal is delivered from the actuatordriving section 39 to the throttle valve actuator 40 so that thethrottle valve actuator 40 pivots the throttle valve 31. In thisinstance, the opening of the throttle valve 31 is fed back to theactuator driving section 39 by the throttle valve opening detectingsection 41 to effect feedback control.

Then, after the throttle valve 31 is pivoted to a predeterminedposition, the actuator driving section 39 no more delivers the drivingsignal, and consequently the throttle valve 31 is stopped at thepredetermined position, thereby completing the automatic cruise modecontrol in the present control cycle.

As the throttle valve 31 is operated to open or close the intake airpath 30 in this manner, the amount of air sucked into the engine 13 andthe amount of fuel supply is also changed. Consequently, a torquesubstantially equal to the aimed torque TOM₃ is produced from the engine13.

The torque produced from the engine 13 in this manner is substantiallyequal to a torque necessary to maintain the speed of the vehicle at theaimed speed which is equal to the actual speed of the vehicle at a pointof time directly after releasing of the accelerator pedal 17 asdescribed hereinabove. Then, by the control at steps E104 to E109described above, the throttle valve 31 is temporarily pivoted, directlyafter releasing of the accelerator pedal 27, to a position of a throttlevalve opening which will maintain the speed of the vehicle directlyafter releasing of the accelerator pedal 27 even when the presentcontrol cycle is not a control cycle which falls on a timing at whichopening or closing movement of the throttle valve 31 is to be performedin order to make preparations for subsequent transition to a constantspeed running condition at the aimed speed.

Such pivotal motion of the throttle valve 31 by the control at stepsE104 to E109 described above is substantially same as pivotal motion ofthe throttle valve 31 by the control at steps C121 and C129 to C132 ofFIG. 10 in the non-direct throttle movement control describedhereinabove, but only the difference resides in requirements forstarting the control.

In case the sequence advances to step E101 either in a control cycleafter such control as described above has been executed in a firstcontrol cycle after releasing of the accelerator pedal 27 or in acontrol cycle in which transition to the automatic cruise mode controlis effected after the treadling of the brake pedal 28 has been cancelledto execute the control at steps C121 and C129 to C132, the sequenceadvances to step E110 because the contact of the accelerator switch 15was in an on-state also in the preceding control cycle. At step E110, itis judged whether or not the position of the acceleration switch 45 inthe present control cycle is different from the position of theacceleration switch 45 in the preceding cycle.

In case the acceleration switch 45 has not been changed over, thesequence advances from step E110 to step E128 at which changing overswitch control regarding the changing over switch 46 is executed.

The changing over switch control at step E128 is executed in accordancewith the flow chart shown at steps F101 to F121 of FIG. 13 principallyby the running condition changing over section 12, final aimed speedsetting section 6 and final aimed speed modification controlling section6a of the control section 25 in order to effect changing over of arunning condition of 5 the vehicle in response to operation of thechanging over switch 44, modification of the final aimed speed of thevehicle when the running condition of the vehicle designated in responseto operation of the changing over switch 44 is either an acceleratedrunning condition or a decelerated running condition, and so on.

Referring to FIG. 13, at first at step F101, it is judged in accordancewith the contact information read in at step A103 of FIG. 8(i) whetheror not the contact of the changing over switch 46 is in an on-state. Incase the changing over switch 46 has not been operated, the contactthereof is not in an on-state, and consequently, the sequence advancesto step F111.

At step F111, the value of a flag I₅ is changed to 0, and then thesequence advances to step F112. The flag I₅ indicates, when it assumes avalue equal to 1, that the contact of the changing over switch 46 was inan on-state in the preceding control cycle.

Then at step F112, the value of the flag I₆ is changed to 0.

The changing over switch control in the present control cycle iscompleted with this in case no operation of the changing over switch 46has been made. The sequence thus advances to step E129 of FIG. 12 atwhich it is judged whether or not the value of a flag I₄ is equal to 1.The value of the flag I₄ is changed to 0 at step C145 of FIG. 10 or atstep E102 of FIG. 12 but is changed to 1 either in case the control whenthe contact of the changing over switch 46 is in an on-state is executedor in case the control when the position of the acceleration switch 45is different from that in the preceding control cycle is executed in thechanging over switch control at step E128. Accordingly, if neither ofthe changing over switch 46 and the acceleration switch 45 is operated,then the value of the flag I₄ is equal to 0, and the sequence thusadvances to step E132 depending upon such judgment at step E129. It isto be noted that, in this instance, the designation by the runningcondition designating section 3 of the controlling section is constantspeed running.

Then at step E132, it is judged, depending upon whether or not the valueof the flag I₆ is equal to 1, whether or not the present control cycleis a first control cycle after the contact of the changing over switch26 has been brought into an on-state. In case the changing over switch46 has not been operated, the contact of the changing over switch 46 isnot yet in an on-state and the flag I₆ has a value equal to 0. Thus, thesequence advances to step E133 at which aimed speed control is executed.

The aimed speed control involves control of changing the speed of thevehicle to approach the aimed speed when constant speed running isdesignated by the running condition designating section 3 and control ofmodifying the present value of the aimed speed by the aimed speedchanging switch 46. The aimed speed control is executed in accordancewith the flow chart of steps J101 to J116 of FIG. 16 principally by theconstant speed controlling section 8 of the control section 25.

In short, in the aimed speed control, it is judged at first at step J101whether or not the value of the flag I₈ is equal to 1. The value of theflag I₈ is changed to 1 at step C128 of FIG. 10 in case treadling of thebrake pedal 26 is cancelled to cause transition to a running conditionof the vehicle by the automatic cruise mode control, but in casetreadling of the accelerator pedal 26 is cancelled to cause transitionto a running condition of the vehicle by the automatic cruise modecontrol, the value of the flag I₈ is changed to 1 at step E106 of FIG.12. Accordingly, in case the sequence advances to step J101 withoutmaking an operation of any of the acceleration switch 45 and thechanging over switch 46 after transition to a running condition of thevehicle by the automatic cruise mode control, the sequence advances tostep J102 depending upon such judgment at step J101.

At step J102, it is judged, depending upon whether or not the value ofthe flag I₁₁ is equal to 1, whether the present control cycle falls on atiming at which opening or closing movement of the throttle valve 31should be performed. In case the value of the flag I₁₁ is equal to 1,the sequence advances to step J103 at which control necessary foropening or closing movement of the throttle valve 31 is executed. To thecontrary, in case the value of the flag I₁₁ is not equal to 1, theautomatic cruise mode control for the present control cycle iscompleted.

After the sequence advances to next step J103 because the value of theflag I₁₁ is equal to 1 at step J102, the actual speed VA read in at stepA103 of FIG. 8(i) is substituted into the aimed speed VS for constantspeed running as a temporary value. Such setting of the aimed speed VSis made in preparation for control after the speed of the vehiclebecomes substantially fixed, and such setting is thus executed beforethe speed of the vehicle becomes substantially constant. The set valueis updated for each control cycle which falls on a timing for opening orclosing movement of the throttle valve 31 until the speed of the vehiclebecomes substantially fixed.

Then at step J104, it is judged whether or not the absolute value of theactual acceleration DVA for which the value of DVA₆₅ or DVA₁₃₀ has beendesignated by the control of steps C141 to C143 of FIG. 10 as describedhereinabove is smaller than a preset reference value Kα, that is,|DVA|<Kα. In case the speed of the vehicle has become substantiallyfixed as a result of the aimed speed control involving reduction inacceleration of the vehicle, |DVA|<Kα is judged at step J104, and thesequence thus advances to step J108 at which the value of the flag I₈ ischanged to 0, whereafter the sequence advances to step J109. To thecontrary, in case the speed of the vehicle has not yet becomesubstantially fixed and the acceleration of the vehicle has not yetdecreased, |DVA|<Kα is not judged at step J104, and the sequence thusadvances to step J105.

At step J105, it is judged, depending upon whether or not the actualacceleration DVA has a positive value, whether the vehicle is either inan accelerated condition or in a decelerated condition. In case theactual acceleration DVA has a positive value, the vehicle is in anaccelerated condition, and accordingly, in order to put the vehicle intoa constant speed running condition, the sequence advances to step J107at which the value of a preset correction amount ΔDV₂ subtracted fromthe actual acceleration DVA is set to the aimed acceleration DVS. To thecontrary, in case the actual acceleration DVA has a negative value, thevehicle is in a decelerated condition, and accordingly, in order to putthe vehicle into a constant speed running condition, the sequenceadvances to step J106 at which the value of the correction amount ΔDV₂added by the actual acceleration DVA is set to the aimed accelerationDVS. The aimed speed control in the present control cycle is completedwith this, and the sequence now advances to step E123 of FIG. 12.

At steps E123 to E127 of FIG. 12, control is executed for making theacceleration of the vehicle coincide with the aimed acceleration DVS.Accordingly, if the control of steps J101 to J107 of FIG. 16 is repeatedbefore the speed of the vehicle becomes substantially fixed, the aimedacceleration DVS gradually approaches 0 so that the absolute value ofthe actual acceleration DVS is decreased and the speed of the vehiclegradually approaches a fixed value.

Then, if |DVA|<Kα is judged at step J104 of FIG. 16, the sequenceadvances to step J109 via step J108 as described hereinabove, and in thecontrol cycle then, the aimed speed VS set at step J103 is used as anaimed speed in the control for constant speed running at step J109 toJ116 described below.

To the contrary, in the following control cycle or cycles subsequent toa control cycle in which the sequence advances to step J109 via stepJ108, the automatic cruise mode control is executed continuously. Then,since the value of the flag I₈ remains 0 unless the acceleration switch45 or the changing over switch 46 is operated, the sequence advances,depending upon such judgment at step J101, to step J109 at which thefollowing control is executed.

At step J109, it is judged in accordance with the contact informationread in at step A103 of FIG. 8(i) whether or not the aimed speedchanging switch 48 of the automatic cruise switch 18 is in a positionturned in the (+) direction in FIG. 6. In case it is judged that the (+)side contact of the aimed speed changing switch 48 is in an on-state,the sequence advances to step J110 at which the value of the aimed speedVS for the preceding control cycle added by a preset correction amountVT₃ is set as a new aimed speed VS, whereafter the sequence advances tostep J113. To the contrary, if the (+) side contact of the aimed speedchanging switch 48 is not in an on-state at step J109, the sequenceadvances to step J111.

At step J111, it is judged whether or not the aimed speed changingswitch 48 is in a position turned in the (-) direction in FIG. 6. Incase the (-) side contact of the aimed speed changing switch 48 is in anon-state, the sequence advances to step J112 at which the value of theaimed speed VS in the preceding control cycle subtracted by thecorrection amount VT₃ is set as a new aimed speed VS, whereafter thesequence advances to step J113. To the contrary, if the (-) side contactof the aimed speed changing switch 48 is not in an on-state at stepJ111, the sequence advances directly to step J113.

By such control at steps J109 to J112 as described above, modificationof the aimed speed VS by the aimed speed changing switch 48 is executed,and if the on-state of the (+) side contact of the aimed speed changingswitch 48 is continued, then the aimed speed VS is increased for eachcontrol cycle by the control at step J110. To the contrary, if theon-state of the (-) side contact of the aimed speed changing switch 48is continued, the aimed speed VS is decreased for each control cycle bythe control at step J112.

Thus, if such modification of the aimed speed VS by the aimed speedchanging switch 48 as described above is executed and then the turningmotion of the in the (+) or (-) direction in FIG. 6 is stoppedwhereafter the aimed speed changing switch 48 is returned to theintermediate stopping position, then the aimed speed VS modified in thejust preceding control cycle will be employed as an aimed speed in thefollowing control cycle or cycles. Accordingly, in case the aimed speedchanging switch 48 is not operated at all after the sequence advancesfrom step J104 to step J109 via step J108, the aimed speed VS set atstep J103 will be employed as an aimed speed in the following controlcycle or cycles.

Such modification of the aimed speed VS by the control at steps J109 toJ112 as described above is performed only after the absolute value ofthe actual acceleration DVA has decreased to a value smaller than thereference value Kα as described above. Accordingly, modification of theaimed speed VS by the aimed speed changing switch 48 is enabled onlywhen the vehicle is in a constant speed running condition after thespeed thereof has become substantially fixed.

Subsequently at step J113, a difference VS-VA between the aimed speed VSand the actual speed VS read in at step A103 of FIG. 8(i) is calculated,whereafter the sequence advances to step J114.

At step J114, control of high stability is required rather than controlof high responsibility because the speed of the vehicle is alreadysubstantially constant. Accordingly, among the three actualaccelerations DVA₆₅, DVA₁₃₀ and DVA₈₅₀ calculated in the interruptcontrol of steps A123 to A128 of FIG. 8(iv) and read in at step A103 ofFIG. 8(i), the actual acceleration DVA₈₅₀ which has a highest stabilityas described hereinabove is designated as a value of the actualacceleration DVA which is to be used at step E123 of FIG. 12 which willbe hereinafter described.

Then at step J115, an aimed acceleration DVS₄ corresponding to thedifference VS-VA between the aimed speed VS and the actual speed VAcalculated at step J113 is found out by control executed in accordancewith the flow chart of steps M101 to M106 of FIG. 18. Then at step J116,the aimed acceleration DVS₄ is substituted as a value of the aimedacceleration DVS which is to be used at step E123 of FIG. 12 which willbe hereinafter described, thereby completing the present aimed speedcontrol. The sequence then advances to step E123 of FIG. 12.

Determination of the aimed acceleration DVS₄ at step J115 is performedin accordance with the flow chart shown in FIG. 18 by the constant speedcontrolling section 8 of the control section 25. Referring to FIG. 18,at first at step M101, an aimed acceleration DVS₃ corresponding to thedifference VS-VA calculated at step J113 of FIG. 16 is read out from amap #MDVS3. The map #MDVS3 is provided to find out an aimed accelerationDVS₃ using the difference VS-VA as a parameter. The difference VS-VA andthe aimed acceleration DVS₃ have such a relationship as illustrated inFIG. 23.

Subsequently at step M102, an acceleration allowance DVMAX correspondingto the difference VS-VA is read out from a map #MDVMAX. The map #MDVMAXis provided to find out an acceleration allowance DVMAX using thedifference VS-VA as a parameter. The difference VS-VA and theacceleration allowance DVMAX have such a relationship as illustrated inFIG. 24.

Then at step M103, the value of the aimed acceleration DVS₃ subtractedby the value of DVS₈₅₀ designated as the actual acceleration DVA at stepJ114 of FIG. 16 (that is, the value of DVS₃ -DVA) is calculated as anacceleration difference DVX. Then at subsequent step M104, it is judgedwhether or not the acceleration difference DVX is smaller than theacceleration allowance DVMAX (DVX<DVMAX).

In case DVX<DVMAX is judged at step M104, the sequence advances to stepM105 at which the aimed acceleration DVS₃ is designated as an aimedacceleration DVS₄. To the contrary, if DVX<DVMAX is not judged at stepM104, the sequence advances to step M106 at which the actual speed DVAadded by the acceleration allowance DVMAX is designated as an aimedacceleration DVS₄.

By making a determination of the aimed acceleration DVS₄ by such controlof steps M101 to M106 as described above, the amount of variation of theaimed acceleration DVS₄ is restricted within the acceleration allowanceDVMAX. Accordingly, a change in acceleration of the vehicle which isperformed to restore a speed of the vehicle which has suddenly changedby some causes during constant speed running of the vehicle will proceedmoderately.

In case the sequence advances to step E123 of FIG. 12 either after theaimed acceleration DVS₄ determined in value by the control of steps M101to M106 has been substituted into the aimed acceleration DVS at stepJ116 of FIG. 16 or after the value of the aimed acceleration DVS hasbeen set by the control of step J106 or J107, an aimed torque TOM₂ ofthe engine 13 necessary to make the acceleration of the vehicle equal tothe aimed acceleration DVS is calculated in accordance with thefollowing equation (5):

    TOM.sub.2 =[{(W·r/g)·ks+ki}·(DVS-DVA)+T.sub.Q ·TEM]/T.sub.Q                                    (5)

It is to be noted that the equation (5) above is substantially same asthe equation (1) or (4) given hereinabove, but, in case the sequenceadvances from step J106 or J107 of FIG. 16 to step E123, DVA in theequation (5) is the value designated by the control of steps C141 toC143 of FIG. 10. To the contrary, in case the sequence advances fromstep J116 of FIG. 16 to step E123, DVA in the equation (5) is DVA₈₅₀designated at step J114 of FIG. 16.

After then, the sequence advances to step E124 at which a throttle valveopening θ_(TH2) corresponding to the aimed torque TOM₂ calculated atstep E123 and the engine rotational speed N_(E) detected by the enginerotational speed detecting section 21 and read in at step A103 of FIG.8(i) is read out from the aforementioned map #MTH (not shown), and thenthe sequence advances to step E125.

The control at steps E123 and E124 is executed commonly by the constantspeed controlling section 8, acceleration controlling section 9 anddeceleration controlling section 10 of the control section 25. Thus, incase the sequence advances from step E133 to step E123, control isexecuted at steps E123 and E124 by the constant speed controllingsection 8 to set a throttle valve opening θ_(TH2) as described above.

Subsequently at step E125, it is judged whether or not the value of theflag I₁₁ is equal to 1. In case I₁₁ =1 is judged, then the sequenceadvances to step E126 because the present control cycle falls on atiming at which opening or closing movement of the throttle valve 31should be performed. To the contrary, if I₁₁ =1 is not judged, thepresent control cycle does not fall on such timing, and accordingly, theautomatic cruise mode control for the present control cycle is completedwithout performing opening or closing movement of the throttle valve 31.

In case the sequence advances to step E126, the throttle valve 31 ispivoted, in a similar manner as at step E109, to a position whichprovides the throttle valve opening θ_(TH2) determined at step E124.Consequently, a torque substantially equal to the aimed torque TOM₂ isproduced from the engine 13. Then, since such opening or closingmovement of the throttle valve 31 in the present control cycle falls ona timing for opening or closing movement, the value of the flag I₁₂ ischanged to 0 at subsequent step E127, thereby completing the automaticcruise mode control in the present control cycle.

As described above, either if treadling of the accelerator pedal 27 iscancelled in a released condition of the brake pedal 28 or if treadlingof the brake pedal 28 is cancelled in a released condition of theaccelerator pedal 27, then transition to a running condition by theautomatic cruise mode control takes place, and then if neither of theacceleration switch 45 and the changing over switch 46 is operated, thenthe throttle valve 31 is temporarily pivoted directly after suchcancelling so that the speed of the vehicle directly after cancelling oftreadling of the accelerator pedal 27 or the brake pedal 28 may bemaintained. Then, after transition to the automatic cruise mode control,the throttle valve 31 is pivoted, for each timing for opening or closingmovement of the throttle valve 31, in accordance with a throttle valveopening set by the constant speed controlling section 8 of the controlsection 25.

In particular, since, even if such pivotal motion of the throttle valve31 that may assure maintenance of the speed of the vehicle directlyafter releasing of the pedal 27 or 28 is performed temporarily withoutwaiting a controlling cycle which falls on a timing for opening orclosing movement of the throttle valve 31 after cancelling of treadingof the pedal 27 or 28, the speed of the vehicle varies to some degreeafter then, the throttle valve 31 is pivoted for each control cyclewhich falls on a timing for opening or closing movement of the throttlevalve 31, thereby reducing variation in speed of the vehicle until asubstantially fixed speed is finally reached.

Accordingly, in case neither of the acceleration switch 45 and thechanging over switch 46 is operated after cancelling of treading of thepedal 27 or 28, the following control takes place except an instancewherein more sudden braking than a reference level by the brake (notshown) continues for an interval of time longer than the referenceinterval of time and the speed of the vehicle upon ending of suchbraking is lower than the reference value.

In short, a throttle valve opening is set by the constant speedcontrolling section (not shown) of the control section 25 so that suchan output power may be obtained from the engine 13 that a speed of thevehicle substantially equal to the speed of the vehicle at a point oftime when the designation by the running condition designating section 3of the control section 25 is changed to constant speed running (at aninstant at which treadling of the pedal is cancelled) can be maintained.Then, the throttle valve 31 is pivoted for each timing for opening orclosing movement thereof in accordance with the throttle valve opening,and as a result, the vehicle makes constant speed running at apredetermined speed.

After the speed of the vehicle has become substantially fixed by suchpivotal motion of the throttle valve 31, it is enabled to modify theaimed speed of the vehicle during constant speed running by operation ofthe aimed speed changing switch 48, and an amount of variation of theaimed speed of the vehicle can be obtained which increases in proportionto the duration of a condition wherein the aimed speed changing switch48 is held turned in the (+) direction or in the (-) direction in FIG.6.

After transition to a running condition of the vehicle by the automaticcruise mode control, if neither of the acceleration switch 45 and thechanging over switch 46 is operated, then the control is such asdescribed above. Now, control when the acceleration switch 45 or thechanging over switch 46 is operated after such transition as describedabove is described.

In case the acceleration switch 45 is operated so that it is changedover to any one of the positions [b] to [d] shown in FIG. 6 after thespeed of the vehicle has become substantially fixed by the controldescribed above after transition to a running condition of the vehicleby the automatic cruise mode control, the sequence advances via stepE101 of FIG. 12 to step E110 at which it is judged whether or not theposition of the acceleration switch 45 has been changed from that in thepreceding control cycle as described hereinabove.

In case the sequence advances to step E110 in a first cycle after theposition of the acceleration switch 45 has been changed, the sequenceadvances, depending upon such judgment at step E110, to step E111 atwhich the value of the flag I₅ is changed to 0 and then to step E112 atwhich the value of a flag I₉ is changed to 0, whereafter the sequenceadvances to step E114. It is to be noted that the flag I₉ indicates,when it assumes a value equal to 1, that control for smoothly raisingthe acceleration of the vehicle to an aimed acceleration set inaccordance with the position of the acceleration switch 45 afterchanging of the designation by the running condition designating section3 of the control section 25 to accelerated running as a result ofoperation of the acceleration switch 45 or the changing over switch 46was executed already in the preceding control cycle.

At step E114, it is judged in accordance with the contact informationread in at step A103 of FIG. 8(i) in the present control cycle whetheror not the position of the acceleration switch 45 is [a] in FIG. 6. Incase it is judged that the position is [a], the sequence advances tostep E115, but on the contrary if it is judged that the position is not[a], then the sequence advances to step E116.

In case the sequence advances to step E116, the designation by therunning condition designating section 3 of the control section 25 hasbeen changed over to accelerated running and the value of the flag I₄ ischanged to 1. Then at step E117, the value of the flag I₈ is changed to0, whereafter the sequence advances to step E118.

It is to be noted that the control cycle then is a first control cycleafter the position of the acceleration 45 has been changed and openingor closing movement of the throttle valve 31 is not yet performed aftersuch changing. Thus, the value of the flag I₁₂ is changed to 0 at stepE118, and then at step E119, the value DVA₆₅ read in at step A103 ofFIG. 8(i) is adopted as a value of the actual acceleration DVA to beused subsequently in the present control cycle from a similar reason asat step E118. After then, the sequence advances to step E120.

At step E120, a final aimed speed VS of the vehicle which is an aimedvalue of the speed of the vehicle after acceleration is set by the finalaimed speed setting section 6 of the control section 25. The value of VSis set to a value of the sum between a preset correction amount VK₁ andthe actual speed VA detected by the speed/acceleration detecting section24 and read in by the control section 25 (refer to step A103 of FIG.8(i)) in the present control cycle.

Then, the sequence advances to step E121 at which the aimed accelerationsetting section 4 of the control section 25 executes acceleration switchcontrol in accordance with the flow chart of steps G101 to G105 shown inFIG. 14. In the acceleration switch control, a value of an aimedacceleration DVS₂ is set in accordance with the position [b], [c] or [d]of the acceleration switch 45 shown in FIG. 6.

In short, it is judged at steps G101 and G103 of FIG. 14 at which one ofpositions [b], [c] and [d] the acceleration switch 45 is, and setting ofthe value of the acceleration DVS₂ is executed at step G102, G104 andG105 for the individual positions [b], [c] and [d].

In particular, referring to FIG. 14, it is judged at first at step G101whether or not the acceleration switch 45 is at the position [b] shownin FIG. 6, and in case the acceleration switch 45 is at the position[b], the sequence advances to step G102 at which a value DVSb set inadvance for the position [b] is substituted into the aimed accelerationDVS₂. To the contrary, in case it is judged at step G101 that theacceleration switch 45 is not at the position [b], the sequence advancesto step G103 at which it is judged whether or not the accelerationswitch 45 is at the position [c] shown in FIG. 6. In case it is judgedthat the acceleration switch 45 is at the position [c], the sequenceadvances to step G104 at which a value DVSc set in advance for theposition [c] is substituted into the aimed acceleration DVS₂.

To the contrary, in case it is judged at step G103 that the accelerationswitch 45 is not at the position [c], this means that the accelerationswitch 45 is at the position [d], and accordingly, a value DVSd set inadvance for the position [d] is substituted into the aimed accelerationDVS₂. It is to be noted that the reason why it can be judged at stepG103 that the acceleration switch 45 is at the position [d] is that ithas been judged already at step E114 of FIG. 12 before the accelerationswitch control is entered that the position of the acceleration switch45 is not [a] and it has been judged already at steps G101 and G103 thatthe position of the acceleration switch 45 is neither [b] nor [c].

Setting of a value of the aimed acceleration DVS₂ corresponding to theposition of the acceleration switch 45 is executed in this manner.However, since the aimed acceleration DVS₂ is an aimed value of theacceleration of the vehicle when it becomes fixed after acceleration hasbeen started as a result of designation of accelerated running by therunning condition designating section 3 of the control section 25, oneof the three accelerated conditions (DVSb, DVSc and DVSd) of the vehicleis selected in accordance with the position [b], [c] or [d] of theacceleration switch 45. Such DVSb, DVSc and DVSd have values having arelationship of DVSb<DVSc<DVSd and corresponding to moderateacceleration, intermediate acceleration and quick acceleration,respectively.

The acceleration switch control is thus completed, and the sequence thenadvances to step E122 of FIG. 12 at which acceleration control isexecuted principally by the acceleration controlling section 9 of thecontrol section 25.

The acceleration control is executed in accordance with the position ofthe acceleration switch 45 when accelerated running is designated by therunning condition designating section 3 of the control section 25 asdescribed hereinabove. In the acceleration control, the acceleration ofthe vehicle is raised smoothly to the aimed acceleration DVS₂ designatedin accordance with the position ([b], [c] or [d]) of the accelerationswitch 45 by the aimed acceleration setting section. By such acceleratedrunning, the change in acceleration is made smooth when the speed of thevehicle reaches the final aimed speed set by the final aimed speedsetting section 6 and the final aimed speed modification controllingsection 6a of the control section 25.

Such acceleration control is executed in accordance with the flow chartillustrated at steps L101 to L121 of FIG. 17.

Referring to FIG. 17, it is judged at first at step L101 whether or notthe actual speed VA read in at step A103 of FIG. 8(i) is greater thanthe preset reference value K₅ (VA>K₅). In case VA>K₅ is judged, thesequence advances directly to step L104, but on the contrary if VA>K₅ isnot judged, the sequence advances to step L104 via steps S102 and L103.

In case the sequence advances from step L101 to L102, an aimedacceleration DVSAC corresponding to the actual speed VA and the positionof the acceleration switch 45 as represented by the contact informationread in at step A103 of FIG. 8(i) is read out from a map #MDVSAC.

The map #MDVSAC is provided to find out an aimed acceleration DVSACusing the actual speed VA and the position of the acceleration switch 45as parameters. The actual speed VA and the position of the accelerationswitch 45 have such a relationship to the aimed acceleration DVSAC asillustrated in FIG. 26.

In particular, while the actual speed VA varies from 0 to the referencevalue K₅, the aimed acceleration DVSAC increases in a correspondingrelationship to an increase of the actual speed VA for each of thepositions [b] to [d] of the acceleration switch 45 shown in FIG. 6.Thus, when the actual speed VA becomes equal to the reference value K₅,the value of the aimed acceleration DVSAC becomes equal to the value ofthe aimed acceleration DVS₂ set for each of the position [b] to [d] ofthe acceleration switch 45 in the acceleration switch control (refer toFIG. 14) at step E121 of FIG. 12.

Then, the sequence advances to step L103 at which the value of the aimedacceleration DVS₂ set by the acceleration switch control is changed toDVSAC read out at step L102, and then the sequence advances to stepL104.

In short, when the speed of the vehicle is higher than the referencevalue K₅, the value of the aimed acceleration DVS₂ remains the value setin the acceleration switch control. To the contrary, when the speed ofthe vehicle is lower than the reference value K₅ as at a time directlyafter starting, the value of the aimed acceleration DVS₂ increases asthe speed increases, and a value smaller than the value set in theacceleration switch control is used as the value of the aimedacceleration DVS₂.

Subsequently at step L104, it is judged whether or not the value of theflag I₁₁ is equal to 1. The flag I₁₁ indicates, when it assumes a valueequal to 1, that the present control cycle falls on a timing at whichopening or closing movement of the throttle valve 31 should be performed(a throttle valve opening/closing timing cycle) as describedhereinabove. In case it is judged at step L104 that the value of theflag I₁₁ is not equal to 1, the acceleration control in the presentcontrol cycle is completed immediately because the present control cycledoes not fall on a throttle valve opening/closing timing cycle.

To the contrary, in case it is judged at step L104 that the value I₁₁ isequal to 1, this means that the present control cycle falls on athrottle valve opening/closing timing cycle, and the sequence advancesto step L105 to continuously execute the acceleration control.

At step L105, it is judged whether or not the value of a flag I₉ isequal to 1. The flag I₉ indicates, when it assumes a value equal to 1,that control at step L108 or L110 which will be hereinafter describedwas executed in the preceding control cycle. In case the sequenceadvances to step L105 for the first time after changing over of theacceleration switch 45 has been effected, it is judged at step L105 thatthe value of the flag I₉ is not equal to 1 because the value of the flagI₉ has been changed to 0 at step E113 of FIG. 12 as describedhereinabove, and the sequence thus advances to step L106.

At step L106, the value of a flag I₁₃ is changed to 0, and then thesequence advances to step L107. The flag I₁₃ indicates, when it assumesa value equal to 1, that an aimed acceleration DVS₁ designated in valueat step L108 or step L110 which will be hereinafter described and theaimed acceleration DVS₂ set in the acceleration switch control do nothave a relationship of DVS₁ <DVS₂.

At subsequent step L107, the value of the flag I₉ is changed to 1, andthen the sequence advance to step L108.

At step L108, a sum of the actual acceleration DVA into which DVS₆₅ hasbeen substituted at step E119 of FIG. 12 and the preset correctionamount ΔDV₁ (DVA+ΔDV₁) is designated as a value of the aimedacceleration DVS₁, and then the sequence advances to step L111.

At step L111, it is judged whether or not the two aimed accelerationsDVS₁ and DVS₂ set in this manner have a relationship of DVS₁ <DVS₂. Incase there is no significant difference between the actual accelerationDVA and the aimed acceleration DVS₂ and consequently it is judged atstep L111 that the aimed acceleration DVS₁ and the aimed accelerationDVS₂ do not have a relationship of DVS₁ <DVS₂, the sequence advances tostep L113 at which the value of the flag I₁₃ is changed to 1, whereafterthe sequence advances to step L114.

To the contrary, in case it is judged at step L111 that the relationshipof DVS₁ <DVS₂ is satisfied, the sequence advances to step L112 at whichthe aimed acceleration DVS₁ is designated as a value of the aimedacceleration DVS which is to be used for accelerated running of thevehicle in the automatic cruise mode control in the present controlcycle.

It is to be noted that, in case the present control cycle is a controlcycle in which the sequence advances to step L105 for the first timeafter the acceleration switch 45 has been changed over to any one of thepositions [b] to [d] in FIG. 6 and further changing over of theacceleration switch 45 is not performed so that the acceleration controlis executed continuously in the following control cycle as describedhereinabove, since the flag I₉ have been changed to 1 in value at stepL107 in the present control cycle, the sequence will advance, in thefollowing control cycle, to step L109 depending upon such judgment atstep L105.

At step L109, it is judged whether or not the value of the flag I₁₃ isequal to 1. Here, in case the sequence advanced from step L111 to stepL113 in one of the preceding cycles to change the value of the flag I₁₃to 1, the sequence now advances from step L109 to L114. To the contrary,in case the sequence did not advance from step L111 to step L113 in thepreceding control cycles, the sequence advances to step L110 because thevalue of the flag I₁₃ is not equal to 1.

At step L110, a sum of the value of the aimed acceleration DVS₁ in thepreceding cycle and the correction amount ΔDV₁ is designated as a newvalue of the aimed acceleration DVS₁, and then the sequence advances tostep L111.

Accordingly, the value of the aimed acceleration DVS₁ is increased inproportion to a time elapsed as the sequence advances repetitively tostep L110 until it is judged at step L109 that the value of the flag I₁₃is equal to 1.

Then, if the aimed acceleration DVS₁ increases until it is judged atstep L111 that the relationship of DVS₁ <DVS₂ is satisfied no more, thesequence now advances from step L111 to L113 at which the value of theflag I₁₃ is changed to 1. Consequently, in the following control cycle,the sequence will advance from step L109 to L114 so that the value ofthe aimed acceleration DVS₁ may not increase any more.

To the contrary, until it is judged at step L111 that the relationshipDVS₁ <DVS₂ is satisfied no more, the aimed acceleration DVS₁ the valueof which increases in such a manner as described above is designated, atstep L112, as a value of an aimed acceleration DVS_(AC) (aimedacceleration designated by the automatic cruise switch), and then atstep L120, the aimed acceleration DVS_(AC) is set as an aimedacceleration DVS which is to be adopted at present, thereby completingthe acceleration control. However, if DVS₁ <DVS₂ is not judged at stepL111, then the sequence will advance to step L114 in the following cycleas described above. Accordingly, such designation of DVS=DVS₁ does nottake place any more.

After the sequence advances to step L114, a difference VS-VA between thefinal aimed speed VS set in value at step E120 of FIG. 12 and the actualspeed VA read in at step A103 of FIG. 8(i) is calculated. Then atsubsequent step L115, an aimed acceleration DVS₃ corresponding to thedifference VS-VA is read out from the map #MDVS3.

The map #MDVS3 is provided to find out an aimed acceleration DVS₃ usingthe difference VS-VA as a parameter as described hereinabove, and thedifference VS-VA and the aimed acceleration DVS₃ have such arelationship as illustrated in FIG. 23.

Then the sequence advances to step L116. At step L116, it is judgedwhether or not the aimed acceleration DVS₂ and the aimed accelerationDVS₃ have a relationship of DVS₂ <DVS₃. Here, if it is judged that therelationship DVS₂ <DVS₃ is satisfied, then the sequence advances to stepL117 at which the aimed acceleration DVS₂ is designated as a value ofthe aimed acceleration DVS_(AC). Then at subsequent step L120, the aimedacceleration DVS_(AC) is set as an aimed acceleration DVS to be adoptedat present, thereby completing the acceleration control. To thecontrary, in case it is judged at step L116 that the relationship DVS₂<DVS₃ is not satisfied, the sequence advances to step L118 at which itis judged by the final condition detecting section 11 of the controlsection 25 whether or not the absolute value |VS-VA| of the differenceVS-VA is smaller than a preset reference value K₄.

As shown in FIG. 23, when the value of the difference VS-VA is equal tothe correction amount VK₁ (correction amount added to the actual speedVA in order to set the final aimed speed VS at step E120 of FIG. 12), anaimed acceleration DVS₃ determined in accordance with the map #MDVS3 hasa greater value than the aimed acceleration DVS₂.

Accordingly, in case the sequence advances to step L116 in a controlcycle in which the sequence has advanced to step L116 for the first timeafter changing over of the acceleration switch 45, the difference VS-VAis substantially equal to the correction amount VK₁. Consequently, DVS₂<DVS₃ is judged at step L116, and the sequence advances to step L117.

To the contrary, if changing over of the acceleration switch 45 does nottake place and the acceleration control is continued to accelerate thevehicle in such a manner as hereinafter described in the followingcontrol cycle, the actual speed VA approaches the final aimed speed VSso that the value of the difference VS-VA decreases. In response to suchdecrease of the difference VS-VA, the aimed acceleration DVS₃ isdecreased as seen in FIG. 23.

Then, if the difference VS-VA becomes smaller than Vα shown in FIG. 23and the aimed acceleration DVS₃ becomes smaller than the aimedacceleration DVS₂, then the sequence advances to step L118 dependingupon such judgment at step L116.

Here, in case it is judged at step L118 that a relationship of|VS-VA|<K₄ is not satisfied, the sequence directly advances to stepL119, but on the contrary if it is judged that the relationship of|VS-VA|<K₄ is satisfied, the sequence advances to step L119 via stepL121 as it is determined that the speed of the vehicle has reached thefinal aimed speed. At step L119, the aimed acceleration DVS₃ isdesignated as a value of the aimed acceleration DVS_(AC), and then atstep L120, the aimed acceleration DVS_(AC) is set as an aimedacceleration DVS to be adopted at present, thereby completing theacceleration control.

Accordingly, in a control cycle after the aimed acceleration DVS₃ hasbecome smaller than the aimed acceleration DVS₂, the aimed accelerationDVS₃ is designated as a value of the aimed acceleration DVS. Since theaimed acceleration DVS is an aimed value of the acceleration uponaccelerated running of the vehicle, after the aimed acceleration DVS₃ isdesignated, the actual acceleration decreases as the actual speed VAapproaches the final aimed speed VS.

After the actual speed VA becomes substantially equal to the final aimedspeed VS, |VS-VA|<K₄ is judged at step L118, and the sequence advancesto step L121 as described hereinabove.

Such judgment detects that the final aimed speed VS has been reached bythe speed of the vehicle as a result of accelerated running. Thus, aftersuch detection is achieved, the value of the flag I₄ is changed to 0 atstep L121 by the running condition changing over section 12 of thecontrol section 25 in order to change the designation by the runningcondition designating section 3 of the control section 25 to constantspeed running at the final aimed speed VS. It is to be noted that theflag I₄ indicates, when it assumes a value equal to 0, that designationof the running condition designating section 3 should be changed toconstant speed running.

After completion of the acceleration control at step E122 of FIG. 12 insuch a manner as described above, the sequence advances to step E123 atwhich an aimed torque TOM₂ of the engine 13 necessary to make theacceleration of the vehicle equal to the aimed acceleration DVS iscalculated as described hereinabove in accordance with the equation (5)given hereinabove.

Then at step E124, a throttle valve opening θ_(TH2) with which the aimedtorque TOM₂ can be obtained from the engine 13 is determined, and thenthe sequence advances to step E125. It is to be noted that, when thedesignation by the running condition designating section 3 of thecontrol section 25 is accelerated running, the control at step E123 andstep E124 is executed by the acceleration controlling section 9 of thecontrol section 25 in such a manner as described hereinabove.

The sequence advances from step E122 to step E125 via steps E123 andE124 in case it is judged at step L104 of FIG. 17 that the value of theflag I₁₁ is equal to 1. Accordingly, I₁₁ =1 is judged at step E125, andthe sequence advances to step E126 at which the throttle valve 31 isactuated to a position provided by the throttle valve opening θ_(TH2) insuch a manner as described hereinabove.

Then at subsequent step E127, the value of the flag I₁₂ is changed to 1,thereby completing the automatic cruise mode control in the presentcontrol cycle.

Since a torque substantially equal to the aimed torque TOM₂ is producedfrom the engine 13 by actuating the throttle valve in such a manner asdescribed, the vehicle makes accelerated running at an accelerationsubstantially equal to the aimed acceleration DVS.

While a control cycle wherein the sequence advances to step E116 viasteps E110 to E114 in such a manner as described above is executed inresponse to changing over of the acceleration switch 45 to one of thepositions [b] to [d] in FIG. 6, if neither of the acceleration switch 45and the changing over switch 46 is operated, the automatic cruise modecontrol will be executed continuously in the following control cycle. Inthis instance, it is judged at first at step E101 of FIG. 12 that thecontact of the accelerator switch 15 has been in an on-state, and thesequence thus advances to step E110. This is because, also in thepreceding cycle, the accelerator pedal 27 was not treadled and theautomatic cruise mode control was executed.

At step E110, it is judged whether or not the position of theacceleration switch 45 has been changed from that in the precedingcontrol cycle as described hereinabove. Here, since the accelerationswitch 45 has not been operated, the judgment is in the negative and thesequence thus advances to step E128 at which the changing over switchcontrol related to the changing over switch 46 is executed.

Such changing over switch control is executed in accordance with theflow chart shown at steps F101 to F121 of FIG. 13 as describedhereinabove.

Referring to FIG. 13, at first at step F101, it is judged whether or notthe contact of the changing over switch 46 is in an on-state. Since herethe changing over switch 46 is not operated, the contact of the changingover switch 46 is not in an on-state, and the judgment at step F101 isin the negative. The sequence thus advances to step F111 at which thevalue of the flag I₅ is changed to 0.

Then at subsequent step F112, the value of the flag I₆ is changed to 0,thereby completing the changing over switch control in the presentcontrol cycle.

It is to be noted that, although described hereinabove, the flag I₅indicates, when it assumes a value equal to 1, that the contact of thechanging over switch 46 was in an on-state in the preceding controlcycle, and the flag I₆ indicates, when it assumes a value equal to 1,that the present control cycle is a first control cycle after thecontact of the changing over switch 46 has been changed to an on-state.

Then, the sequence advances to step E129 of FIG. 12 at which it isjudged whether or not the value of the flag I₄ is equal to 1. The flagI₄ indicates, when it assumes the value equal to 0, that the designationby the running condition designating section 3 of the control section 25should be constant speed running as described hereinabove. Since herethe value of the flag I₄ was changed to 1 at step E116 in the firstcontrol cycle after changing over of the acceleration switch 45 to anyone of the positions [b] to [d] shown in FIG. 6, so long as theaccelerated running of the vehicle continues, the judgment at step E129remains in the affirmative, and the sequence advances to step E130.

To the contrary, if the vehicle is accelerated until the running speedreaches the final aimed speed VS as described hereinabove, the value ofthe flag I₄ is changed to 0 at step L120 of FIG. 17 by the runningcondition changing over section 12 of the control section 25.Consequently, the judgment at step E129 becomes in the negative, and thesequence advances to step E132. It is to be noted that, in thisinstance, the designation by the running condition designating station 3of the control section 25 is changed over to constant speed running.

To the contrary, in case the sequence advances from step E129 to stepE130, it is judged at step E130 whether or not the position of theacceleration switch 45 is [a]. Since here at step E130 the accelerationswitch 45 is at any one of the positions [b] to [d], the judgment is inthe negative, and the sequence advances to step E121 at whichacceleration switch control is executed.

The acceleration switch control is executed in accordance with the flowchart shown at steps G101 to G105 of FIG. 14 by the aimed accelerationsetting section 4 of the control section 25 to accomplish setting of anaimed acceleration DVS₂ corresponding to the position of theacceleration switch 45 as described hereinabove.

Then at step E122, acceleration control is executed in accordance withthe flow chart shown at steps L101 to L120 of FIG. 17 principally by theacceleration controlling section 9 of the control section 25 to effectsetting of an aimed acceleration DVS for acceleration running of thevehicle as described hereinabove. In case such setting of an aimedacceleration is effected when the present control cycle falls on atiming at which opening or closing movement is to be performed, openingor closing movement of the throttle valve 31 is subsequently performedat steps E123 to E127 as described hereinabove so that the vehicle makesaccelerated running at an acceleration substantially equal to the aimedacceleration DVS.

After the running speed of the vehicle reaches the final aimed speed VSas a result of accelerated running, the designation by the runningcondition designating section 3 of the control section 25 is changedover to constant speed running as described hereinabove, and then thesequence advances from step E129 to step E132. At step E132, it isjudged whether or not the value of the flag I₆ is equal to 1. Since theflag I₆ has been changed to 0 in value at step F112 of FIG. 13, thesequence advances from step E132 to step E133 at which aimed speedcontrol is executed.

The aimed speed control is executed in accordance with the flow chartshown at steps J101 to J116 of FIG. 16 principally by the constant speedcontrolling section 8 of the control section 25 as describedhereinabove.

In short, since the value of the flag I₈ has been changed to 0 in thefirst control cycle after changing over of the acceleration switch 45(refer to step E117 of FIG. 12), I₈ is not judged at step J101, andconsequently, the sequence advances normally to J109 unless either theacceleration switch 45 or the changing over switch 46 is operated.

The control which is to be executed at steps J109 to J116 subsequentlyis such as described hereinabove, and setting of a value of the aimedacceleration DVS for making the running speed of the vehicle coincidewith the aimed speed VS and for maintaining the same at a fixed level isaccomplished.

After completion of the aimed speed control, opening or closing movementof the throttle valve 31 is performed at steps E123 to E127 of FIG. 12as described hereinabove so that the vehicle makes constant speedrunning at a running speed substantially equal to the aimed speed VS.

Accordingly, after the final aimed speed VS has been reached by therunning speed of the vehicle as a result of acceleration of the vehicleby changing over of the acceleration switch 45 to any one of thepositions [b] to [d] shown in FIG. 6, the final aimed speed VS isregarded as an aimed speed, and the running speed of the vehicle ismaintained constant at the aimed speed after then.

In case the changing over switch 45 is changed to change the designationby the running condition designating section 3 of the control section 25to accelerated running and the vehicle is accelerated at an aimedacceleration DVS designated in the acceleration control at step E122,the aimed acceleration DVS and the running speed of the vehicle exhibitsuch variations, for example, as illustrated in FIGS. 27(i) and 27(ii) ,respectively. It is to be noted that FIG. 27(i) illustrates a variationin value of the aimed acceleration DVS with respect to a time elapsedafter such changing over of the changing over switch 45 while FIG.27(ii) illustrates a variation in value of the running speed of thevehicle with respect to a time elapsed after changing over of thechanging over switch 45.

In short, if the vehicle is running at first at a constant running speedv1 and the acceleration switch 45 is changed over to any one of thepositions [b] to [d] at a certain point of time t₀ as shown in FIGS.27(i) and 27(ii), then accelerated running is designated. Then,acceleration is started with the aimed acceleration the value of whichhas been set by the step L108 of FIG. 17. In this instance, since theaimed acceleration DVS₁ set at step L110 of FIG. 17 is set to the aimedacceleration DVS for accelerated running for each control cycle whichfalls on a timing at which opening or closing of the throttle valve 31is to be performed, the aimed acceleration DVS will be increased foreach such control cycle in such a stepwise condition as seen in FIG.27(i).

Meanwhile, as the aimed acceleration DVS increases in this manner, therunning speed of the vehicle begins to increase smoothly at the point oftime t₀.

As a result, the aimed acceleration DVS₁ will finally become higher, ata point of time t₁, than the aimed acceleration DVS₂ set in accordancewith the position of the acceleration switch 45 by the aimedacceleration setting section 4 of the control section 25. Consequently,in a control cycle after the point of time t₁, the aimed accelerationDVS₂ is employed as a value of the aimed acceleration DVS. Accordingly,the aimed acceleration DVS thereafter presents a fixed value as seen inFIG. 27(i), and consequently, the running speed of the vehicle willincrease substantially at a fixed rate as seen in FIG. 27(ii).

Then, after the running speed reaches, at a point of time t₂, a valuesmaller by Vα shown in FIG. 23 than the final aimed speed VS set at stepE120 of FIG. 12, the aimed speed DVS₃ read out at step L115 of FIG. 17from the map #MDVS3 presents a smaller value than the aimed accelerationDVS₂. Then, in a control cycle after the point of time t₂, the aimedacceleration DVS₃ is employed as a value of the aimed acceleration DVS.

Since the aimed acceleration DVS₃ decreases as the difference VS-VAbetween the final aimed speed VS and the actual speed VA as shown inFIG. 23 decreases, as the running speed increases, the aimedacceleration DVS gradually decreases for each control cycle in such astepwise condition as shown in FIG. 27(i).

Due to such decrease of the aimed acceleration DVS, the rate of rise ofthe running speed is gradually moderated as seen in FIG. 27(ii).

Then, if it is judged after a point of time t₃ by the final conditiondetecting section 11 of the control section 25 that the differencebetween the running speed and the final aimed speed VS is smaller thanthe reference value K₄, changing over to constant speed runningdesignated by the running condition designating section 3 is executed bythe running condition changing over section 12 of the control section25, thereby completing the accelerated running of the vehicle. In acontrol cycle after the point of time t₃, constant speed running of thevehicle is performed by the constant speed controlling section 8 of thecontrol section 25 at the aimed acceleration set in the aimed speedcontrol at step E133 of FIG. 12.

As a result, the running speed smoothly approaches the final aimed speedVS and reaches a value substantially equal to the final aimed speed VSat the point of time t₃, and after the point of time t₃, the runningspeed presents a substantially same value as the final aimed speed VS asseen in FIG. 27(ii). Meanwhile, the aimed acceleration DVS presents avalue near 0 at the point of time t₃, and after the point of time t₃,the aimed acceleration DVS presents a value for maintaining the runningspeed at a value coincident with the final aimed speed VS.

The control when the acceleration switch 45 is changed over to any oneof the positions [b] to [d] shown in FIG. 6 but the changing over switch46 is not operated proceeds in such a manner as described above.Subsequently, description will be given of control which is executedwhen the changing over switch 46 is operated while such acceleratedrunning of the vehicle as described hereinabove is still continued.

If the changing over switch 46 is pulled forwardly in FIG. 6 into anon-state, then the sequence advances from step E101 to step E110 shownin FIG. 12 in a similar manner as described hereinabove. Since theposition of the acceleration switch 45 has not been changed from that inthe preceding control cycle, the judgment at step E110 is in thenegative, and the sequence thus advances to step E128. At step E128,changing over switch control is executed in accordance with the flowchart of steps F101 to F121 shown in FIG. 13 as described hereinabove.

In the changing over switch control, at first at step F101, it is judgedin accordance with the contact information read in at step A103 of FIG.8(i) whether or not the contact of the changing over switch 46 is in anon-state. In this instance, since an operating portion 18a of theautomatic cruise switch 18 is at a forwardly pulled position in FIG. 6,it is judged that the contact of the changing over switch 46 is in anon-state, and the sequence advances to step F102.

At step F102, the value of the flag I₃ is changed to 1, and then atsubsequent step F103, it is judged whether or not the value of the flagI₅ is equal to 1. It is to be noted that the flag I₅ indicates, when itassumes a value equal to 1, that the contact of the changing over switch46 was in an on-state in the preceding control cycle as describedhereinabove.

In case the sequence advances to step F103 in a first control cycleafter the contact of the changing over switch 46 has been changed intoan on-state, since the value of the flag I₅ has been changed to 0 atstep F111 in the control cycle before changing over of the contact ofthe changing over switch 46 into an on-state, the sequence advances tostep F104 depending upon such judgment at step F103. Then at step F104,the value of the flag I₅ is changed to 1, whereafter the sequenceadvances to step F105.

When the sequence advances from step F105 to step F104 as describedhereinabove, a flag I₆ is set to 1. It is to be noted that the flag I₆indicates, when it assumes a value equal to 1, that the present cycle isa first control cycle after the contact of the changing over switch 46has been changed into an on-state as described hereinabove.

To the contrary, in case the contact of the changing over switch 46 wasalready in an on-state in the preceding control cycle, the value of theflag I₅ has been changed to 1 at step F104 in the preceding controlcycle. Accordingly, the sequence advances to step F113 depending uponsuch judgment at step F103.

At step F106 subsequent to step F105, the value of the flag I₁₂ ischanged to 0, and then the sequence advances to step F107. It is to benoted that, although described hereinabove, the flag I₁₂ indicates, whenit assumes a value equal to 0, either that opening or closing movementof the throttle valve 31 has not yet been performed in a control cyclewhich falls on a timing for opening or closing movement of the throttlevalve 31 which is encountered for the first time after enteringautomatic cruise mode control in a control cycle, or that, although suchopening or closing movement has been performed, opening or closingmovement of the throttle valve 31 has not been performed in a controlcycle which falls on a timing for opening or closing movement of thethrottle valve 31 which is first encountered after modification of thedesignation by the running condition designating section 3 of thecontrol section 25 as a result of operation of the acceleration switch45 or the changing over switch 46.

At step F107, since the present control cycle is a first control cycleafter the contact of the changing over switch 46 has been changed to anon-state, a running condition different from the running condition ofthe vehicle which has been designated by the running conditiondesignating section (not shown) till the preceding control cycle isdesignated. To this end, giving preference to the superiority infollow-up performance to an actual acceleration value, DVA₆₅ read in atstep A103 of FIG. 8(i) is used as the value of the actual accelerationDVA.

At subsequent step F108, it is judged whether or not the value of a flagI₄ is equal to 1. It is to be noted that the flag I₄ indicates, when itassumes a value equal to 0, that constant speed running should bedesignated by the running condition designating section (not shown).

Here, since the contact of the changing over switch 46 has been changedover to an on-state while the accelerated running of the vehicledesignated by changing over of the acceleration switch 45 stillcontinues, the present control cycle is a first control cycle after thecontact of the changing over switch 46 has been changed into an on-stateand accordingly the value of the flag I₄ is not changed after it hasbeen changed to 1 at step E116 of FIG. 12. Accordingly, I₄ =1 is judgedat step F108, and the sequence thus advances to step F109.

At step F109, the value of the flag I₄ is changed to 0 by the runningcondition changing over section 12 of the control section 25, and thenthe sequence advances to step F110. At step F110, the latest actualspeed VA_(I) found out in the interrupt control of steps A123 to A128 ofFIG. 8(iv) is read in, thereby completing the changing over switchcontrol in the present control cycle.

After the changing over switch control at step E128 of FIG. 12 has beenexecuted in such a manner as described above, the sequence advances tosubsequent step E129 at which it is judged whether or not the value ofthe flag I₄ is equal to 1. Since the flag I₄ has been changed to 0 invalue at step F109 of FIG. 13, I₄ =1 is not judged at step E129, and thesequence thus advances to step E132 so that the designation by therunning condition designating section 3 of the control section 25 ischanged over to constant speed running.

At step E132, it is judged whether or not the value of the flag I₆ isequal to 1 (I₆ =1). Since the value of the flag I₆ has been changed to 1at step F105 of FIG. 13, I₆ =1 is judged at step E132, and the sequenceadvances to step E105.

The control at step E105 and steps E106 to E109 following the step E105is quite the same as the control executed at steps E105 to E109 in thefirst control cycle after releasing of the accelerator pedal 27described hereinabove. Accordingly, in the present control (E105 toE109), irrespective of whether or not the present control cycle falls ona timing for opening or closing movement of the throttle valve 31, thethrottle valve 31 is pivoted to a throttle valve opening with which itis forecast that constant speed running can be assured with an aimedspeed defined by the actual speed VA_(I) upon changing over of thechanging over switch 46. As a result, a torque substantially equal to adesired torque (of a magnitude required for constant speed running) isproduced from the engine 13, and the running condition of the vehiclebegins to change from accelerated running to constant speed running.

Such control as described above is executed in the first control cycleafter the contact of the changing over switch 46 has been changed to anon-state. However, in case the acceleration switch 45 is not operatedwhile the automatic cruise mode control is executed continuously in thefollowing control cycle, the sequence advances via steps E101 and E110of FIG. 12 to step E128 to execute changing over switch control in asimilar manner as described above.

The changing over switch control is executed also in accordance with theflow chart shown in steps F101 to F121 of FIG. 13 as describedhereinabove. In case the sequence advances from step F101 to step F102,however, since the contact of the changing over switch 46 continues inan on-state and the value of the flag I₅ remains 1 after having beenchanged to 1 at step F104 in the first control cycle after changing overof the contract of the changing over switch 46 to an on-state, thesequence advances to step F113 depending upon judgement at step F103whether or not the value of the flag I₅ is equal to 1.

At step F113, it is judged whether or not the value of the flag I₄ isequal to 1. Since the flag I₄ has been changed to 0 in value at stepF109 in the control cycle after the contact of the changing over switch46 has been changed to an on-state, I₄ =1 is not judged at step F113,and the sequence thus advances to step F112. Then at step F112, thevalue of the flag I₆ is changed to 0, thereby completing the changingover switch control in the present control cycle.

Meanwhile, in case the sequence advances from step F101 to step F111,the value of the flag I₅ is changed to 0 at step F111, and then thevalue of the flag I₆ is changed to 0 at step F112, thereby completingthe changing over switch control in the present control cycle.

Accordingly, the changing over switch control when the contact of thechanging over switch 46 remains in an on-state continuously after thepreceding control cycle and the changing over switch control when thecontact of the changing over switch 46 is changed over from an on-statein the present control cycle are different only in setting of the valueof the flag I₅.

In case the sequence advances to step E129 of FIG. 12 subsequently aftercompletion of the changing over switch control, it is judged at stepE129 whether or not the value of the flag I₄ is equal to 1. Here, sincethe flag I₄ has been changed to 0 at step F109 of FIG. 13 and remains asit is, the sequence advances to step E132 depending upon such judgmentat step E129. Consequently, the designation by the running conditiondesignating section 3 of the control section 25 remains constant speedrunning.

At step E132, it is judged whether or not the value of the flag I₆ isequal to 1. Here, since the value of the flag I₆ has been changed to 0at step F112 of FIG. 13, the sequence advances from step E132 to stepE133 at which aimed speed control is executed.

The aimed speed control is executed in accordance with the flow chartshown at steps J101 to J116 of FIG. 16 as described hereinabove.

Referring to FIG. 16, it is judged at first at step J101 whether or notthe value of the flag I₈ is equal to 1. The flag I₈ indicates, when itassumes a value equal to 0, that the vehicle is running substantially ata constant speed by the automatic cruise mode control. Here, since thevalue of the flag I₈ has been changed to 1 when the sequence advancedfrom step E132 via step E105 to step E106 of FIG. 12 in the firstcontrol cycle after changing over of the changing over switch 46 to anon-state as described hereinabove, the sequence advances to step J102depending upon such judgment at step J101.

Control which is executed at steps J102 to J107 is quite the same as thecontrol executed in the aimed speed control at step E133 in thefollowing cycles after execution of the control at steps E101 to E109 ofFIG. 12 in the first control cycle after releasing of the acceleratorpedal 27.

In particular, setting of an aimed acceleration DVS necessary togradually reduce the actual acceleration DVS is performed for eachthrottle valve opening/closing cycle.

Control at steps E123 to E127 which is executed after completion of suchaimed speed control is similar to that described hereinabove. Thus, foreach throttle valve opening/closing timing cycle, the throttle valve 31is opened or closed to such a throttle valve opening (openingadjustment) with which an acceleration of the vehicle equal to the aimedacceleration DVS can be obtained.

As a result, the acceleration of the vehicle is decreased gradually, andthe running speed of the vehicle gradually approaches the actual speedVA_(I) at a point of time when constant speed running is reached afterturning on of the contact of the changing over switch 46 so that it soonbecomes substantially fixed.

Then, if it is judged at step J104 of FIG. 16 that the absolute value|DVA| of the actual acceleration DVA is smaller than the presetreference value Kα, then the value of the flag I₈ is changed to 0 atsubsequent step J108, whereafter control is executed at steps J109 toJ116.

Also the control at steps J109 to J116 is quite the same, similarly tothe control at steps J101 to J107, as the control which is executed inthe aimed speed control at step E133 of FIG. 12 when the automaticcruise mode control is executed as a result of releasing of theaccelerator pedal 17. To the contrary, in a control cycle after acontrol cycle in which the judgment at step J104 is made, since thevalue of the flag I₈ has been changed at step J108, the sequence willadvance from step J101 to J109 to execute similar control.

In particular, after the running speed of the vehicle has becomesubstantially fixed, setting of an aimed acceleration DVS necessary tomaintain the running speed constant is executed. To the contrary, incase the aimed speed changing switch 48 is changed over to the (+) sideor the (-) side in FIG. 6, the set value of the aimed speed VS isincreased or decreased in response to such changing over in order tomaintain the running speed constant.

Further, by control at steps E123 to E127 which is executed aftercompletion of the aimed speed control, the throttle valve 31 is openedor closed to a required throttle valve opening (throttle valve openingwith which an acceleration of the vehicle equal to the aimedacceleration DVS can be obtained) as described hereinabove. As a result,the vehicle makes constant speed running at a constant running speedsubstantially coincident with the aimed speed.

As described so far, if the contact of the changing over switch 46 ischanged to an on-state when accelerated running of the vehicle is beingperformed, then the designation by the running condition designatingsection 3 of the control section 25 is changed over to constant speedrunning, and the actual speed VA_(I) at a point of time when thechanging over takes place is used as an aimed speed for constant speedrunning.

Then, as a result of releasing of the accelerator pedal 27, the runningspeed of the vehicle is maintained substantially constant in a similarmanner as in the case of transition to a constant speed runningcondition.

In the following, description will be given of control when theoperating portion 18a of the automatic cruise switch 18 is pulledforwardly to put the contact of the changing over switch 46 into anon-state while the designation by the running condition designatingsection 3 is constant speed running in the automatic cruise mode controlwith the acceleration switch 45 positioned at any one of the positions[b] to [d] shown in FIG. 6.

In this instance, after the contact of the changing over switch 46 ischanged to an on-state, the sequence advances from step E101 to stepE110 of FIG. 12 in a similar manner as in the case describedhereinabove. At step E110, since operation of the switch 45 has nottaken place, it is judged that the position of the acceleration switch45 has not been changed from that in the preceding control cycle, andthe sequence advances to step E128.

At step E128, changing over switch control is executed in accordancewith the flow chart shown at steps F101 to F121 of FIG. 13 as describedhereinabove.

In short, at first at step F101, it is judged in accordance with thecontact information read in at step A103 of FIG. 8(i) whether or not thecontact of the changing over switch 46 is in an on-state, and thesequence advances to step F102 depending upon judgment at step F101.

At step F102, the value of the flag I₃ is changed to 1, and then thesequence advances to step F103 at which it is judged whether or not thevalue of the flag I₅ is equal to 1. In the preceding cycles, theautomatic cruise mode control was executed without operation of theacceleration switch 45 or the changing over switch 46, and the value ofthe flag I₅ has been changed to 0 at step F111. Accordingly, in thefirst control cycle after the contact of the changing over switch 46 hasbeen changed to an on-state, the sequence advances to step F104depending upon judgement at step F103. Then, the value of the flag I₅ ischanged to 1 at step F104, and the sequence advances to step F105.

It is to be noted that, in case the contact of the changing over switch46 remains in an on-state to continue the automatic cruise mode controlin which the sequence advances to step F103 in the following controlcycle, the sequence then advances to step F113 depending upon judgmentat step F103 because the flag I₅ has been changed to 1 at step F104 inthe first control cycle after changing over of the changing over switch46 to an on-state as described hereinabove.

Then, in case the sequence advances from step F103 via step F104 to stepF105, the value of the flag I₅ is changed to 1 at step F105, and thenthe value of the flag I₁₂ is changed to 0 at subsequent step F106,whereafter the sequence advances to step F107.

At step F107, since the present control cycle is a first control cycleafter the contact of the changing over switch 46 has been changed to anon-state, a running condition different from the running condition ofthe vehicle which has been held designated till the preceding controlcycle is designated by the running condition designating section 3 ofthe control section 25. To this end, giving preference here to thesuperiority in follow-up performance to an actual acceleration value,DVA₆₅ read in at step A103 of FIG. 8(i) is used as the value of theactual acceleration DVA.

At subsequent step F108, it is judged whether or not the value of theflag I₄ is equal to 1.

Here, in case the acceleration switch 45 has been changed over to effectaccelerated running of the vehicle and then the running condition of thevehicle has entered a constant speed running condition at a final aimedspeed as described hereinabove, the value of the flag I₄ has beenchanged to 0 at step L120 of FIG. 17.

To the contrary, in case the automatic cruise mode control has beenexecuted to enter a constant speed running condition of the vehicle as aresult of releasing of the accelerator pedal 27, the value of the flagI₄ has been changed to 0 at step E102 of FIG. 12. On the other hand, incase the automatic cruise mode control has been executed to enter aconstant speed running condition of the vehicle as a result of releasingof the brake pedal 28, the value of the flag I₄ has been changed to 0 atstep C145 of FIG. 10.

Further, in case the contact of the changing over switch 46 was changedinto an on-state to enter a constant speed running condition of thevehicle, the value of the flag I₄ has been changed to 0 at step F109 ofFIG. 13.

Accordingly, I₄ =1 is not judged at step F108, and the sequence advancesto step F117.

At step F117, the value of the flag I₄ is changed to 1, and then at stepF118, the value of the flag I₉ is changed to 0. Subsequently at stepF119, it is judged in accordance with the contact information read in atstep A103 of FIG. 8(i) whether or not the acceleration switch 45 is atthe position [a] shown in FIG. 6.

Since the acceleration switch 45 is positioned at one of the positions[b] to [d] shown in FIG. 6 then, the sequence advances to step F121depending upon such judgment at step F117. At step F121, the designationby the running condition designating section 3 of the control section 25is changed over to accelerated running.

In particular, at step F121, a value of a sum (VA+VK₁) of the actualspeed VA detected by the speed/acceleration detecting section 24 andread in at step A103 of FIG. 8(i) in the preceding control cycle and thesame preset correction amount VK₁ as used at step E120 of FIG. 12described hereinabove is set as a final aimed speed VS for acceleratedrunning.

The changing over switch control in the preceding control cycle iscompleted with this.

In this manner, in the changing over switch control, a final aimed speedVS for accelerated running is set in a similar manner as in a case whenthe acceleration switch 45 is changed over to one of the positions [b]to [d] shown in FIG. 6 in a constant speed running condition of thevehicle.

After the changing over switch control at step E128 of FIG. 12 has beenexecuted in such a manner as described above, the sequence subsequentlyadvances to step E129 at which it is judged whether or not the value ofthe flag I₄ is equal to 1. Since the flag I₄ has been changed to 1 invalue at step F117 of FIG. 13 as described hereinabove, the sequenceadvances to step E130 depending upon such judgment at step E129.

At step E130, it is judged in accordance with the contact informationread in at step A103 of FIG. 8(i) whether or not the position of theacceleration switch 45 is [a] in FIG. 6. Here, since the position of theacceleration switch 45 is one of the positions [b] to [d] shown in FIG.6, it is judged at step E130 that the acceleration switch 45 is not atthe position [a], and the sequence advances to step E121.

At step E121, acceleration switch control is executed by the aimedacceleration setting section 4 of the control section 25, and then thesequence advances to step E122 at which acceleration control is executedprincipally by the acceleration controlling section 9 of the controlsection 25.

Such acceleration switch control and acceleration control caused byoperation of the changing over switch 46 are the same as theacceleration switch control and the acceleration control, respectively,which are executed when the acceleration switch 45 is changed over tocause designation of an accelerated running condition of the vehicle.Further, control which is executed in a first control cycle afteroperation of the changing over switch 46 is the same as the controlwhich is executed in a first control cycle after changing over of theacceleration control switch 45 to cause designation of an acceleratedrunning condition of the vehicle. Besides, control in a control cyclewhich falls on a timing for opening or closing movement of the throttlevalve 31 which is first encountered after operation of the changing overswitch 46 is the same as the control in a control cycle which falls on atiming for opening or closing movement of the throttle valve 31 which isfirst encountered after changing over of the acceleration switch 45 tocause designation of an accelerated running condition of the vehicle.

In particular, in a first control cycle after operation of the changingover switch 46, setting of an aimed acceleration DVS₂ for a constantacceleration running condition corresponding to a position of theacceleration switch 45 is executed in the acceleration switch control,and then when the actual speed VA is lower than the preset referencevalue K₅, the value of the aimed acceleration DVS₂ is changed to a valuecorresponding to the actual speed in the subsequent accelerationcontrol.

To the contrary, in case the control cycle falls on a timing for openingor closing movement of the throttle valve 31, the preset correctionamount ΔDV₁ is added to the actual acceleration DVA additionally by theacceleration control, and the value of DVA+ΔDV₁ is set as an aimedacceleration DVS for assuring smooth starting of accelerated running ofthe vehicle.

In case a first control cycle after the contact of the changing overswitch 46 has been changed over to an on-state falls on a timing foropening or closing movement of the throttle valve 31, the throttle valve31 is opened or closed in such a manner as described above at steps E123to E127 after completion of the acceleration control. Consequently,acceleration of the vehicle is started at an acceleration substantiallyequal to the aimed acceleration DVS.

To the contrary, in case the first control cycle does not fall on suchopening/closing timing, the automatic cruise mode control in the controlcycle is completed without effecting setting of an aimed accelerationDVS by the acceleration control in the control cycle or opening orclosing movement of the throttle valve 31 at steps E123 to E127.

Control in a first control cycle after the contact of the changing overswitch 46 has been changed to an on-state is executed in such a manneras described so far. However, in case neither of the accelerator pedal27 and the brake pedal 28 is treadled to continuously execute theautomatic cruise mode control nor the acceleration switch 45 is changedover in the following control cycle, the sequence advances again viasteps E101 and E110 of FIG. 20 to step F101 of FIG. 20 at which it isjudged whether or not the contact of the changing over switch 46 is inan on-state in a similar manner as described hereinabove.

Then, in case the contact of the changing over switch 46 remains in anon-state continuously from the preceding control cycle, the sequenceadvances to step F102 depending upon judgment at step F101. Theoperating portion 18a of the automatic cruise switch 18 is released toallow the automatic cruise switch 18 to be returned to its initialposition. To the contrary, in case the contact of the changing overswitch 46 is in an off-state, the sequence advances to step F111depending upon such judgment at step F101.

In case the sequence advances from step F101 to F102, the value of theflag I₃ is changed to 1 at step F102, and then the sequence advances tostep F103 at which it is judged whether or not the value of the flag I₅is equal to 1. Since the value of the flag I₅ has been changed to 1 atstep F104 in the first control cycle after changing over of the contactof the changing over switch 46 into an on-state as described hereinaboveand the contact still remains in an on-state, the sequence advances tostep F113 depending upon such judgment at step F103.

At step F113, it is judged whether or not the value of the flag I₄ isequal to 1. Since the value of the flag I₄ has been changed to 1 at stepF117 in the present control cycle, the sequence advances to step F114depending upon such judgment at step F113.

At step F114, it is judged in accordance with the contact informationread in at step A103 of FIG. 8(i) whether the acceleration switch 45 isat the position [a] shown in FIG. 6. Now, since the acceleration switch45 is at any one of the positions [b] to [d] shown in FIG. 6, thesequence advances to step F116 depending upon such judgment at stepF114.

At step F116, a value of a sum VS+VT₁ of the final aimed speed VS in thepreceding control cycle and a preset correction amount VT₁ is designatedas a final aimed value VS for accelerated running in the present controlcycle by the final aimed speed modification controlling section 6a ofthe control section 25.

It is to be noted that the final aimed speed VS in the preceding controlcycle has been designated in value at step F121 in case the presentcontrol cycle is a first control cycle after changing over of thecontact of the changing over switch 46 to an on-state, but in case thepresent control cycle is not such a first cycle, the final aimed speedVS has been designated in value at step F116.

Accordingly, if the contact of the changing over switch 46 is changed toan on-state, then a value of the actual speed VA added by a presetcorrection amount VK₁ is designated as a final aimed speed VS foraccelerated running in a subsequent first control cycle. If the on-stateof the changing over switch 46 is continued, as the duration continues,the final aimed speed VS is increased by a preset correction amount VT₁for each control cycle.

Then, in case the sequence advances from step F116 to step F112, thevalue of the flag I₆ is changed to 0, thereby completing the changingover switch control in the present control cycle.

In case the contact of the changing over switch 46 is not in an on-statein the present control cycle and the sequence advances to step F111depending upon such judgment of step F101, the value of the flag I₅ ischanged to 0 at step F111, and then the sequence advances to step F112.At step F112, the value of the flag I₆ is changed to 0 as describedhereinabove, thereby completing the changing over switch control in thepresent control cycle.

After completion of the changing over switch control in this manner, thesequence subsequently advances to step E129 of FIG. 12. At step E129, itis judged whether or not the value of the flag I₄ is equal to 1. Sincethe value of the flag I₄ has been changed to 1 at step F117 of FIG. 13,the sequence advances to step E130 depending upon such judgment at stepE129.

At step E130, it is judged whether or not the acceleration switch 45 isat the position [a] in FIG. 6. Since here the acceleration switch 45 isat one of the positions [b] to [d] shown in FIG. 6, the sequenceadvances from step E130 to step E121.

Control to be executed at step E121 and subsequent steps E122 to E127 isthe same as the control which is executed in the second and followingcontrol cycles after the acceleration switch 45 has been changed asdescribed hereinabove.

In particular, in the acceleration switch control at step E121, sincethere is no change in position of the acceleration switch 45, a valueset in the first control cycle after the changing over switch 46 hasbeen changed to an on-state is set as an aimed acceleration DVS₂ forsubsequent constant acceleration running.

Further, by the acceleration control at step E122, the acceleration ofthe vehicle is raised smoothly to the aimed acceleration DVS₂ uponstarting of such acceleration, whereafter the vehicle is accelerated atthe aimed acceleration DVS₂, and when the running speed of the vehiclereaches the final aimed speed VS, the aimed acceleration DVS is set sothat the acceleration may be decreased gradually before the final aimedspeed VA is reached.

Further, if the actual speed VA is lower than the preset reference valueK₅ then, the aimed acceleration DVS₂ is modified to a valuecorresponding to the actual speed VA. Then, the throttle valve 31 isopened or closed in accordance with such aimed acceleration DVS for eachthrottle valve opening/closing timing cycle. Consequently, the vehiclewill be accelerated at an acceleration substantially equal to the aimedacceleration DVS.

Also in case the running speed of the vehicle has become substantiallyequal to the final aimed speed VS as a result of such accelerationdescribed just above, the value of the flag I₄ is changed to 0 in theacceleration control at step E122 similarly as in the case when theacceleration control is executed as a result of changing over of theacceleration switch 45. Accordingly, in the following control cycle, thesequence will advance from step E129 via step E132 to step E133 at whichconstant speed running of the vehicle is performed in the aimed speedcontrol in which the final aimed speed VS is employed as an aimed speed.

As described so far, in case the acceleration switch 45 is held at oneof the positions [b] to [d] shown in FIG. 6 so that the automatic cruisemode control is executed and the vehicle is in a constant speed runningcondition, if the operating portion 18a of the automatic cruise switch18 is pulled forwardly in FIG. 6 to change the contact of the changingover switch 45 to an on-state, then the designation by the runningcondition designating section 3 of the control section 25 is changed toaccelerated running. Consequently, accelerated running of the vehicle isperformed smoothly at an acceleration corresponding to the position ofthe acceleration switch 45 in a similar manner as in the case ofchanging over of the acceleration switch 45.

Meanwhile, the final aimed speed upon such accelerated running is set toa higher value by a predetermined amount than the running speed of thevehicle in the constant speed running condition, and such final aimedspeed is increased as the time while changing over switch 46 is held atthe forwardly pulled position in FIG. 6 passes.

Then, after the running speed of the vehicle reaches the final aimedspeed as a result of such accelerated running, the designation by therunning condition designating section 3 is changed over to constantspeed running, and consequently, constant speed running of the vehicleis performed with an aimed speed defined by the final aimed speed.

While the control when the acceleration switch 45 is changed to one ofthe positions [b] to [d] and the control when the operating portion 18aof the automatic cruise switch 18 is pulled forwardly to change thecontact of the changing over switch 46 to an on-state with theacceleration switch 45 positioned at one of the positions [b] to [d]have been described above, control when the acceleration switch 45 ischanged to the position [a] and control when the operating portion 18aof the automatic cruise switch 18 is pulled forwardly to change thecontact of the changing over switch 46 to an on-state with theacceleration switch 45 positioned at the position [a] will be describedbelow.

If the acceleration switch 45 is changed over to the position [b] shownin FIG. 6, or if the contact of the changing over switch 46 is changedto an on-state with the acceleration switch 46 positioned at theposition [b] and accordingly the vehicle is in a constant speed runningcondition, an accelerated running condition of the vehicle isdesignated. Then, in case the acceleration switch 45 is changed over tothe position [b] while acceleration of the vehicle is proceeding, sincethe accelerator pedal 27 was not treadled also in the preceding controlcycle, it is judged at step E101 of FIG. 12 that the contact of theaccelerator switch 15 was in an on-state in the preceding control cycle.The sequence thus advances to step E110.

At step E110, it is judged in accordance with the contact informationread in at step A103 of FIG. 8(i) whether or not the position of theacceleration switch 45 has been changed from that in the precedingcontrol cycle as described hereinabove. Since the acceleration 45 was atthe position [b] in the preceding control cycle but is at the position[a] in the present control cycle, the sequence advances to step E111depending upon such judgment at step E110.

At step E111 and following steps E112 and E113, the value of the flag I₃is changed to 1 and the values of the flags I₅ and I₉ are changed to 0,respectively. Then at step E114, it is judged in accordance with thecontact information read in at step A103 of FIG. 8(i) whether or not theacceleration switch 45 is at the position [a].

Since the acceleration switch 45 is at the position [a] in the presentcontrol cycle, the sequence advances from step E114 to step E115 atwhich the value of the flag I₄ is changed to 0, whereafter the sequenceadvances to step E104.

Control at step E104 and following steps E105 to E109 is quite the sameas the control at steps E104 to E109 executed in the first control cycleafter releasing of the accelerator pedal 27 described hereinabove.

By the control, irrespective of whether the present control cycle fallson a timing for opening or closing movement of the throttle valve 31,the vehicle is controlled such that constant speed running may beperformed with an aimed speed defined by the actual speed VA_(I) at apoint of time directly after the acceleration switch 45 has been changedover to the position [a]. More particularly, the throttle valve 31 isadjusted to a suitable throttle valve opening so that a torque necessaryfor such constant speed running may be produced from the engine 13. As aresult, torque of a desired magnitude is produced from the engine 13 sothat the running condition of the vehicle starts changing fromaccelerated running to constant speed running.

Such control as described above is executed in a first control cycleafter the acceleration switch 45 has been changed over to the position[a], and also in the following control cycle, the automatic cruise modecontrol is executed continuously. Then, in case the acceleration switch45 is held at the position [a] and the changing over switch 46 is notoperated, the sequence advances from step E101 to step E110 of FIG. 12in a similar manner as described hereinabove in order to judge whetheror not the position of the acceleration switch 45 has been changed fromthat in the preceding control cycle.

Since the acceleration switch 45 is held at the position [a] and theposition thereof has not been changed from that in the preceding controlcycle as described hereinabove, the sequence advances from step E110 tostep E128 at which changing over switch control is executed.

The changing over switch control is executed in accordance with the flowchart shown at steps F101 to F121 of FIG. 13 as described hereinabove.

Thus, at first step F101, since the changing over switch 46 has not beenoperated, it is judged that the contact of the changing over switch 46is not in an on-state as described hereinabove, and the sequenceadvances to step F111.

At step F111, the value of the flag I₅ is changed to 0, and then at stepF112, the value of the flag I₆ is changed to 0, thereby completing thechanging over switch control in the present control cycle.

Then, the sequence advances to step E129 of FIG. 12, and it is judged atstep E129 whether or not the value of the flag I₄ is equal to 1. Sincethe flag I₄ has been changed to 0 in value at step E115 of the firstcontrol cycle after the acceleration switch 45 has been changed to theposition [a], the sequence advances, depending upon such judgment atstep E129, to step E132 at which the designation by the runningcondition designating section 3 of the control section 25 is changedover to constant speed running.

At step E132, it is judged whether or not the value of the flag I₆ isequal to 1. Since the flag I₆ has been changed to 0 in value at stepF112 of FIG. 13, the sequence advances, depending upon such judgment atstep E132, to step E133 at which aimed speed control is executed.

The aimed speed control is executed in accordance with the flow chart atsteps J101 to J116 of FIG. 16 as described hereinabove.

In short, at first at step J101, it is judged whether or not the valueof the flag I₈ is equal to 1. Since the flag I₈ has been changed to 1 invalue at step E106 of FIG. 12 in the first control cycle after theacceleration switch 45 has been changed to the position [a], thesequence advances from step J101 to step J102.

Control at step J102 and following steps J103 to J107 are quite the sameas the aimed speed control executed at steps J102 to J107 after thesequence has advanced to step E133 in the control cycle following thefirst control cycle after releasing of the accelerator pedal 27 in whichthe control at steps E101 to E109 of FIG. 12 was executed. Inparticular, setting of an aimed acceleration DVS necessary to graduallydecrease the actual acceleration DVA is executed for each control cyclewhich falls on a timing at which opening or closing movement of thethrottle valve 31 is to be performed.

After the aimed speed control is completed in this manner, control issubsequently executed at steps E123 to E127 of FIG. 12 in such a manneras described for the various controls described hereinabove. Thus,opening or closing movement of the throttle valve 31 to such a throttlevalve opening with which an acceleration of the vehicle equal to theaimed acceleration DVS may be obtained is performed for each controlcycle which falls on a timing for such opening or closing movement. As aresult, the acceleration of the vehicle decreases gradually so that therunning speed gradually approaches the actual speed VA_(I) directlyafter changing over of the acceleration switch 45 and becomessubstantially fixed.

The acceleration of the vehicle decreases in this manner. Then, if it isjudged at step J104 of FIG. 16 that the absolute value |DVA| of theactual acceleration DVA is smaller than the preset reference value Kα,then the value of the flag I₉ is changed to 0 at subsequent step J108,whereafter the sequence advances to step J109. Thus, control is executedat step J109 and following steps J110 to J116. To the contrary, in eachcontrol cycle after judgment at step J104 has been made, since the valueof the flag I₉ has been changed to 0 at step J108, the sequence advancesfrom step J101 to step J109 to execute similar control.

The control executed at steps J109 to J116 is quite the same as thecontrol which is executed at steps J109 to J116 after the sequence hasadvanced to step J108 particularly depending upon judgment at step J104in the control which is executed at steps J101 to J108 as describedhereinabove in the automatic cruise mode control after releasing of theaccelerator pedal 27.

Subsequently, control is executed at steps E123 to E127 of FIG. 12. Bythe control, opening or closing movement of the throttle valve 31 tosuch a throttle valve opening with which an acceleration of the vehicleequal to the aimed acceleration DVS can be obtained is performed foreach throttle opening/closing timing cycle. As a result, the vehiclemakes constant speed running at a constant running speed substantiallyequal to the aimed speed VS.

In case the acceleration switch 45 is changed over to the position [a]when accelerated running of the vehicle is effected as a result ofchanging over of the acceleration switch 45 or changing of the contactof the changing over switch 46 to an on-state, the designation by therunning condition designating section 3 of the control section 25 ischanged over to constant speed running, and control is executed forcausing the vehicle to run at a constant speed employing as an aimedspeed the actual speed VA_(I) at a point of time directly after changingover of the acceleration switch 45, that is, the speed of the vehiclewhen the designation of the running condition was changed over toconstant speed running.

The control is similar to that when the running condition is changedover to a constant speed running condition as a result of releasing ofthe accelerator pedal 27 or when the contact of the changing over switch46 is changed to an on-state while the vehicle is making acceleratedrunning. As a result, the running speed of the vehicle is maintainedsubstantially constant in conformity with the aimed speed of thevehicle.

It is to be noted that, since the acceleration switch 45 is at theposition [b] and the designation by the running condition designatingsection 3 of the control section 25 is constant speed running, if theacceleration switch 45 is changed over to the position [a] when thevehicle is in a constant speed running condition, similar control asdescribed hereinabove is executed. In this instance, since thedesignation is already constant speed running from before such changingover, constant speed running is continued at the same fixed speed, andno change takes place in running condition of the vehicle.

Subsequently, description will be given of control to be executed whenthe operating portion 18a of the automatic cruise switch 18 is pulledforwardly in FIG. 6 to change the contact of the changing over switch 46to an on-state while the acceleration switch 45 is held at the position[a] so that the automatic cruise mode control is executed and thevehicle is in a constant speed running condition because the designationby the running condition designating section 3 of the control section 25is constant speed running.

In this instance, if the contact of the changing over switch 46 ischanged over to an on-state, the sequence advances to steps E101 to E110of FIG. 12 in a similar manner as described hereinabove. Since operationof the acceleration switch 45 has not performed at step E110, it isjudged that the position of the acceleration switch 45 has not beenchanged from that in the preceding control cycle, and the sequenceadvances to step E128.

At step E128, changing over switch control is executed as describedhereinabove. Thus, at first at step F101 of FIG. 13, it is judged inaccordance with the contact information read in at step A103 of FIG.8(i) whether or not the contact of the changing over switch 46 is in anon-state.

Since the contact of the changing over switch 46 is now in an on-state,the sequence advances from step F101 to step F102 at which the value ofthe flag I₃ is changed to 1. Then at step F103, it is judged whether ornot the value of the flag I₅ is equal to 1.

In the first control cycle after changing over of the contact of thechanging over switch 46 to an on-state, automatic cruise mode controlwas executed in such a condition wherein neither of the accelerationswitch 45 and the changing over switch 46 has been operated in theproceeding control cycle. Accordingly, the value of the flag I₅ waschanged to 0 at step F111. Consequently, the sequence advances to stepF104 depending upon such judgment at step F103.

At step F104, the value of the flag I₅ is changed to 1, and then at stepF105, the value of the flag I₆ is changed to 1, whereafter the value ofthe flag I₁₂ is changed to 0 at step F106, and then the sequenceadvances to step F107.

At step F107, since the present control cycle is a first control cycleafter the contact of the changing over switch 46 has been changed to anon-state, a running condition different from the running condition whichwas designated in the preceding control cycle is designated by therunning condition designating section 3 of the control section 25. Thus,giving preference to the superiority in follow-up performance to anactual value, DVA₆₅ read in at step A103 of FIG. 8(i) is used as thevalue of the actual acceleration DVA.

At subsequent step F108, it is judged whether or not the value of theflag I₄ is equal to 1. Here, the value of the flag I₄ is equal to 0 asdescribed hereinabove.

In short, in case the constant speed running condition of the vehiclebefore the contact of the changing over switch 44 was changed to anon-state arose from changing over of the acceleration switch 44, thevalue of the flag I₄ has been changed to 0 at step E115 of FIG. 12.

To the contrary, in case such constant speed running condition wasentered as a result of releasing of the accelerator pedal 27, the valueof the flag I₄ has been changed to 0 at step E102 of FIG. 12.

On the other hand, in case such constant speed running condition wasentered as a result of releasing of the brake pedal 28, the value of theflag I₄ has been changed to 0 at step C145 of FIG. 10.

Further, in case such constant speed running condition was entered as aresult of changing over of the contact of the changing over switch 46 toan on-state, the value of the flag I₄ has been changed to 0 at step F109of FIG. 13.

Accordingly, in any case, the sequence advances to step F117 dependingupon such judgment at step F108.

Then at step F117, the value of the flag I₄ is changed to 1, and then atstep F118, the value of the flag I₉ is changed to 0, whereafter thesequence advances to step F119. At step F119, it is judged in accordancewith the contact information read in at step A103 of FIG. 8(i) whetheror not the acceleration switch 45 is at the position [a].

In this instance, since the acceleration switch 45 is at the position[a], the sequence advance, depending upon such judgment at step F119, tostep F120 at which the designation by the running condition designatingsection 3 of the control section 25 is changed over to deceleratedrunning.

In particular, at step F120, a value of the actual speed VA read in atstep A103 of FIG. 8(i) which is subtracted by the present correctionamount VK₂ is determined as a final aimed speed for deceleration runningby the final aimed speed setting section 6 of the control section 25.The changing over switch control in the present control cycle iscompleted with this.

After the sequence subsequently advances to step E129 of FIG. 12, it isjudged whether or not the value of the flag I₄ is equal to 1. Since thevalue of the flag I₄ has been changed to 1 at step F117 of FIG. 13, thesequence advances from step E129 to step E130.

At step E130, it is judged in accordance with the contact informationread in at step A103 of FIG. 8(i) whether or not the acceleration switch45 is at the position [a]. Since the acceleration switch 45 is now atthe position [a], the sequence advances from step E130 to step E131 atwhich deceleration control is executed.

In the deceleration control, setting of an aimed acceleration DVS of anegative value (that is, an aimed deceleration DVS) for causingdecelerated running of the vehicle in which the running speed of thevehicle is decreased to the final aimed speed VS. The decelerationcontrol is executed in accordance with the flow chart shown at stepsH101 to H110 of FIG. 15 principally by the deceleration controllingsection 10 and the aimed acceleration setting section 4 of the controlsection 25.

In short, at first at step H101, it is judged whether or not theabsolute value |VS-VA| of the difference between the final aimed speedVS and the actual speed VA read in at step A103 of FIG. 8(i) is smallerthan the preset reference value K₄.

In case the sequence advances to step H101 in a first control cycleafter the contact of the changing over switch 46 has been changed to anon-state, since the final aimed speed VS is a value obtained bysubtracting the correction amount VK₂ from the actual speed VA asdescribed hereinabove, the absolute value |VS-VA| is equal to thecorrection amount VK₂. Besides, since the correction amount VK₂ is setgreater than the reference value K₄, the relationship of |VS-VA|>K₄ issatisfied, and the sequence thus advances to step H102.

At step H102, a difference VS-VA between the final aimed speed VS andthe actual speed VA is calculated, and then at step H103, an aimedacceleration DVS₅ corresponding to the difference VS-VA is read out froma map #MDVS5. Subsequently at step H104, the aimed acceleration DVS₅ isdesignated as a value of the aimed acceleration DVS for decelerationrunning, thereby completing the deceleration control in the presentcontrol cycle.

The map #MDVS5 mentioned above is provided to find out an aimedacceleration DVS₅ corresponding to an aimed deceleration fordeceleration running using the difference VS-VA as a parameter. Thedifference VS-VA and the aimed acceleration DVS₅ have such arelationship as illustrated in FIG. 25. Accordingly, so long as thedifference VS-VA has a positive value, the aimed acceleration DVS₅ has anegative value and substantially is a deceleration.

After setting of an aimed acceleration DVS by such deceleration controlas described above, the sequence advances to step E123 of FIG. 12. Atstep E123, as described hereinabove, an aimed torque TOM₂ of the engine13 necessary to make the acceleration of the vehicle equal to the aimedacceleration DVS is calculated using the equation (5) given hereinabove.

In the case of a first control cycle after the contact of the changingover switch 46 has been changed to an on-state, since the aimedacceleration DVS₅ having a negative value is designated as an aimedacceleration DVS and the running condition of the vehicle in thepreceding control cycle was constant speed running, the actualacceleration DVA is substantially equal to 0. Accordingly, in thisinstance, an aimed torque TOM₂ calculated in accordance with theequation (5) has a smaller value than the actual torque TEM which isbeing produced by the engine 13.

Then, the sequence advances to step E124 at which a throttle valveopening θ_(TH2) corresponding to the aimed torque TOM₂ calculated atstep E123 and the engine rotational speed N_(E) read in at step A103 ofFIG. 8(i) is read out from the map #MTH (not shown), whereafter thesequence advances to step E125.

It is to be noted that the control at steps E123 and E124 is executed bythe deceleration controlling section 10 of the control section 25because the designation by the running condition designating section 3of the control section is decelerated running.

The minimum value of the throttle valve opening θ_(TH2) of the map #MTH(not shown) corresponds to a minimum opening of the throttle valve 31which provides an engine idling position. Thus, in case the aimed torqueTOM₂ is decreased to a value lower than a minimum torque which can beproduced by the engine 13, the minimum opening is designated for thethrottle valve opening θ_(TH2).

Further, control at step E125 and following steps E126 and E127 is thesame as that which is executed in the various controls describedhereinabove. Thus, in case the present control cycle falls on a timingfor opening or closing movement of the throttle valve 31, the throttlevalve 31 is opened or closed to the throttle valve opening θ_(TH2)designated at step E124, and the value of the flag I₁₂ is changed to 1.

As a result, in case the aimed torque TOM₂ is higher than the minimumtorque which can be produced by the engine 13, a torque substantiallyequal to the aimed torque TOM₂ is produced from the engine 13. On thecontrary, in case the aimed torque TOM₂ is lower than the minimum torquefrom the engine 13, the throttle valve 31 is held at the minimum openingcorresponding to the engine idling position. Consequently, decelerationby engine brake is started so that the running condition of the vehicleis changed from constant speed running to decelerated running.

On the other hand, in case the present control cycle does not fall on atiming for opening or closing movement of the throttle valve 31, theautomatic cruise mode control in the present control cycle is completedwithout making opening or closing movement of the throttle valve 31.

After such control in the first control cycle after the contact of thechanging over switch 46 has been changed to an on-state is executed insuch a manner as described above, the automatic cruise mode control isexecuted continuously in the following control cycle. In case changingover of the acceleration switch 45 takes place, the sequence advancesvia steps E101 and E110 of FIG. 12 in a similar manner as describedhereinabove again to step F101 of FIG. 13 at which it is judged whetheror not the contact of the changing over switch 46 is in an on-state.

In case the contact of the changing over switch 46 is held in anon-state continuously from the preceding control cycle, the sequenceadvances to step F102. To the contrary, in case the operating portion18a of the automatic cruise switch 18 has been released to change thecontact of the changing over switch 46 to an off-state, the sequenceadvances to step F111.

In case the sequence advances from step F101 to F102, the sequencesubsequently advances from step F102 via steps F103 and F113 to stepF114 in a similar manner as in the case when the contact of the changingover switch 46 is continuously held in an on-state in the second andfollowing control cycles after designation of an accelerated runningcondition of the vehicle as a result of changing the contact of thechanging over switch 46 to an on-state while the acceleration switch 45was at one of the positions [b] to [d] as described hereinabove.

At step F114, it is judged in accordance with the contact informationread in at step A103 of FIG. 8(i) whether or not the acceleration switch45 is at the position [a]. Since here the acceleration switch 45 is atthe position [a], the sequence advances to step F115.

At step F115, a value of a difference VS-VT₂ of the preset correctionamount VT₂ from the final aimed speed VS in the preceding control cycleis set as a final aimed speed VS for the present control cycle by thefinal aimed speed modifying section 6a of the control section 25.

It is to be noted that the final aimed speed VS in the preceding controlcycle was set in value at step F120 in case the preceding control cyclewas a first control cycle after changing of the contact of the changingover switch 46 to an on-state but was set in value at step F115 in casethe present control cycle was not such first control cycle.

Accordingly, if the contact of the changing over switch 46 is changedover to an on-state, then in a first control cycle after then, a value(VA-VK₂) of the preset correction amount VK₂ subtracted from the actualspeed VA is designated as a final aimed speed VS for subsequentdecelerated running, and then if the on-state of the contact iscontinued, the final aimed speed VS is decreased by the presetcorrection amount VT₂ for each control cycle as the time passes. Inshort, VS=VA-VT₂ -VK₂.

Subsequently, the sequence advances from step F115 to step F112 at whichthe value of the flag I₆ is changed to 0, thereby completing thechanging over switch control in the present control cycle.

Since the contact of the changing over switch 46 is not in an on-statein the present control cycle, in case the sequence advances from stepF101 to step F111, the value of the flag I₅ is changed to 0 at stepF111, and then the value of the flag I₆ is changed to 0 at subsequentstep F112, thereby completing the changing over switch control in thepreceding control cycle.

After the changing over switch is completed in this manner, the sequenceadvances to step E129 of FIG. 12. At step E129, it is judged whether ornot the value of the flag I₄ is equal to 1 as described hereinabove.Since here the value of the flag I₄ has been changed to 1 at step F117of FIG. 13, the sequence advances to step E130 depending upon suchjudgment at step E129.

At step E130, it is judged whether or not the position of theacceleration switch 45 is [a] shown in FIG. 6. Since here theacceleration switch 45 is at the position [a], the sequence advances tostep E131 to continue the deceleration control described hereinabove.

It is to be noted that the deceleration of the vehicle presents asubstantially equal value to the absolute value of the aimedacceleration DVS, but if the aimed torque TOM₂ calculated at step E123presents a smaller value than the minimum torque which can be producedfrom the engine 13, then the deceleration of the vehicle is a maximumdeceleration obtained by engine brake and is not always equal to thevalue of the aimed acceleration DVS because the throttle valve 31 isclosed to its minimum opening for the engine idling position.

The aimed acceleration DVS₅ set as a value of the aimed accelerationhas, as shown in FIG. 25, a fixed value while the difference VS-VAbetween the final aimed speed VS and the actual speed VA is smaller thanVβ shown in FIG. 25, but where the difference VS-VA is smaller than Vβ,the value of the aimed acceleration DVS₅ approaches 0 as the differenceVS-VA decreases. Accordingly, after the actual speed VA is reduced to avalue near the final aimed speed VS as a result of decelerated running,the degree of deceleration of the vehicle is moderated as the actualspeed VA decreases. Consequently, the running speed of the vehiclesmoothly approaches the final aimed speed.

Decelerated running of the vehicle is accomplished in such a manner asdescribed above. Then, if the actual speed VA is decreased until theabsolute value |VS-VA| becomes smaller than the reference value K₄, itis detected by the final condition detecting section 11 of the controlsection 25 that the running speed of the vehicle has reached the finalaimed speed VS. The sequence thus advances to step H105 depending uponsuch judgment at step H101.

At step H105, a difference VS-VA between the final aimed speed VS andthe actual speed VA is calculated. Then at step H106, giving preferenceto the superiority in stability than the superiority in follow-upperformance because the running speed of the vehicle is substantiallyconstant and there is no sudden change in running condition similarly inthe control of transition to a constant speed running conditiondescribed hereinabove, the actual acceleration DVA₈₅₀ calculated in theinterrupt control of FIG. 8 (iv) and read in at step A103 of FIG. 8 (i)is used as a value of the actual acceleration DVA to be used at stepE123 of FIG. 12.

The sequence subsequently advances to step H107 at which an aimedacceleration DVS₄ is found out in place of the aimed acceleration DVS₅in control executed in accordance with the flow chart at steps M101 toM106 of FIG. 18 because the actual speed VA has become substantiallyequal to the final aimed speed VS and it has been detected by the finalcondition detecting section 11 of the control section 25 that therunning speed of the vehicle has reached the final aimed speed VS asdescribed hereinabove.

Contents of the control are quite the same as those of the controlexecuted at step J115 of FIG. 16 when the accelerator pedal 27 isreleased so that a constant speed running condition by the automaticcruise mode control is entered.

Subsequently at step H108, the aimed acceleration DVS₄ is designated asa value of the aimed acceleration DVS to be used subsequently at stepE123 of FIG. 12, whereafter the sequence advances to step H109.

The aimed acceleration DVS₄ is set in accordance with such arelationship to the difference VS-VA between the aimed speed VS forconstant speed running and the actual speed VA read in at step A103 ofFIG. 8 (i) as illustrated in FIG. 23 or 24 as described hereinabove. Ineither case, the aimed acceleration DVS₄ has a relationship that itincreases as the difference VS-VA increases. Accordingly, the aimedacceleration DVS here acts to stop a decreasing condition of the runningspeed of the vehicle and maintain the running speed of the vehicle atthe aimed speed VS, that is, the final aimed speed VS in the deceleratedrunning condition.

At step H109, the value of the flag I₄ is changed to 0 by the runningcondition changing over section 12 of the control section 25, and thenat step H110, the value of the flag I₈ is changed to 0, therebycompleting the deceleration control in the present control cycle. Afterthen, control is executed at steps E123 to E127 of FIG. 12.

The control is the same as the control at steps E123 to E127 in thevarious cases described hereinabove. Here, the control at steps E123 andE124 is executed by the deceleration controlling section 10 of thecontrol section 25 because the designation by the running conditiondesignating section 3 of the control section 25 is decelerated running.

In particular, a throttle valve opening θ_(TH2) is set in accordancewith the aimed acceleration DVS designated in value in the decelerationcontrol, and in case the present control cycle falls on anopening/closing timing for the throttle valve 31, the throttle valve 31is opened or closed to the throttle valve opening θ_(TH2). As a result,the running speed of the vehicle will remain at a value substantiallyequal to the aimed speed VS.

In this manner, the automatic cruise mode control is executed at stepsH105 to H110 of FIG. 15 continuously in the following control cycle.Further, in case neither of the acceleration switch 45 and the changingover switch 46 is operated, the sequence advances via steps E101 andE110 of FIG. 12 to step F101 of FIG. 13 again in a similar manner asdescribed hereinabove.

Since here the contact of the changing over switch 46 has already beenchanged to an off-state, the sequence advances to step F111 dependingupon such judgment at step F101 as described hereinabove. At step F111,the value of the flag I₅ is changed to 0, and then the value of the flagI₆ is changed to 0 at subsequent step F112, thereby completing thechanging over switch control in the present control cycle.

Then, the sequence advances to step E129 of FIG. 12. At step E129, it isjudged whether or not the value of the flag I₄ is equal to 1. Since thevalue of the flag I₄ has been changed to 0 at step H109 of FIG. 15 asdescribed hereinabove, the sequence advances to step E132 so that thedesignation by the running condition designating section 3 of thecontrol section 25 is changed over to constant speed running.

In particular, while it is judged at step E132 whether or not the valueof the flag I₆ is equal to 1, since the value of the flag I₆ has beenchanged to 0 at step F112 of FIG. 13 as described hereinabove, thesequence now advances from step E132 to step E133 at which aimed speedcontrol is executed.

While the aimed speed control is executed in accordance with the flowchart shown at steps J101 to J116 of FIG. 16, since the value of theflag I₈ which is to be judged at first step J101 has been changed to 0already at step H110 of FIG. 15 as described hereinabove, the aimedspeed control is executed in accordance with the steps J109 to J116 in asimilar manner as in the case wherein the running condition of thevehicle changes over from an accelerated running condition to a constantspeed running condition.

After completion of the aimed speed control, control is executed inaccordance with steps E123 to E127 of FIG. 12 so that the throttle valve31 is opened or closed for each control cycle falling on anopening/closing timing in accordance with the aimed acceleration DVS ina similar manner as described hereinabove. Consequently, the vehiclewill run at a constant running speed substantially equal to the aimedspeed VS.

As described so far, while the operating portion 18a of the automaticcruise switch 18 is pulled forwardly to put the contacts of thechange-over switch 46 into an on-state when the acceleration switch 45is held at the position [a] so that automatic cruise mode control isexecuted and the vehicle is in a constant speed running condition,decelerated running is designated by the running condition designatingsection 3 of the control section 25, and consequently, the running speedof the vehicle is decreased to a final aimed speed VS which decreases invalue as the duration of an on-state of the contacts of the change-overswitch 46 increases. Then, when it is detected by the final conditiondetecting section 11 of the control section 25 that the running speedreaches the final aimed speed VS, the running condition change-oversection 12 of the control section 25 changes over the designation of therunning condition designating section 3 to constant speed running sothat running of the vehicle smoothly changes to constant speed runningwherein the final aimed speed VS is an aimed speed. Consequently, thevehicle thereafter runs at a running speed substantially equal to thefinal aimed speed VS, that is, the running speed at a point of time whenthe designation of the running condition designating section 3 ischanged over to constant speed running.

Subsequently, description will be given of control when the operatingportion 18a of the automatic cruise switch 18 is pulled forwardly inFIG. 6 again to change the contact of the changing over switch 46 to anon-state while such decelerated running as described above stillcontinues.

In this instance, after the contact of the changing over switch 46 ischanged to an on-state, the sequence advances via steps E101 and E110 ofFIG. 12 to step F101 of FIG. 13 in a similar manner as describedhereinabove.

At step F101, it is judged in accordance with the contact informationread in at step A103 of FIG. 8(i) whether or not the contact of thechanging over switch 46 is in an on-state. Since the contact is in anon-state now, the sequence advances to step F102.

At step F102, the value of the flag I₃ is changed to 0, and then at stepF103, it is judged whether or not the value of the flag I₅ is equal to1.

In case the sequence advances to step F103 in a first control cycleafter the contact of the changing over switch 46 has been changed to anon-state, since the value of the flag I₅ has been changed 0 at step F111in the preceding control cycle, the sequence advances to step F104depending upon such judgment at step F103.

At step F104 and following steps F105 and F106, the values of the flagsI₅ and I₆ are changed to 1 and the value of the flag I₁₂ is changed to0, respectively, and then the sequence advances to step F107. At stepF107, the contact of the changing over switch 46 is changed to anon-state as described hereinabove.

Then, since the present control cycle is a first control cycle after thedesignation by the running condition designating section 3 of thecontrol section 25 has been changed to a different running condition,DVA₆₅ read in at step A103 of FIG. 8(i) is used, giving preference tothe superiority in follow-up performance to an actual value, as thevalue of the actual acceleration DVA.

At subsequent step F108, it is judged whether or not the value of theflag I₄ is equal to 1. Since the contact of the changing over switch 46was changed over to an on-state while decelerated running of the vehiclewas still continued and the present control cycle is a first cycle aftersuch changing over of the contact of the changing over switch 46 into anon-state as described hereinabove, the value of the flag I₄ has beenchanged to 1 at step F117 in the changing over switch control of FIG. 13upon reading in of the changing over switch 46. Accordingly, thesequence advances to step F109 depending upon such judgment at stepF108.

At step F109, the value of the flag I₄ is changed to 0 by the runningcondition changing over section 12 of the control section 25, and thenat subsequent step F110, the latest speed VA_(I) found out in theinterrupt control at steps A123 to A128 of FIG. 8(iv) is read in as anactual speed of the vehicle at a point of time directly after thecontact of the changing over switch 46 has been changed to an on-state,thereby completing the changing over switch control in the presentcontrol cycle.

Such changing over switch control as described above is the same as thechanging over switch control in the first control cycle after thecontact of the changing over switch 46 has been changed over to anon-state during accelerated running of the vehicle describedhereinabove. Accordingly, the values of the flags I₄ and I₆ aftercompletion of the changing over switch control are the same. Thus, aftercompletion of the changing over switch control, the sequence advancesvia steps E129 and E132 of FIG. 12 to step E105 at which the designationby the running condition designating section 3 of the control section 25is changed over to constant speed running.

The control at steps E105 to E109 is quite the same as the controlexecuted at steps E105 to E109 in the first control cycle afterreleasing of the accelerator pedal 27 or in the first cycle afterchanging over of the contact of the changing over switch 46 into anon-state during accelerated running of the vehicle. In particular,irrespective of whether or not the present control cycle falls on atiming for opening or closing movement of the throttle value 31, thethrottle valve opening 31 is adjusted so as to effect constant speedrunning of the vehicle using as an aimed speed the actual speed VA_(I)at a point of time directly after the contact of the changing overswitch 46 has been changed to an on-state.

As a result, a required torque is produced from the engine 13 so thatthe running condition of the vehicle starts to change from deceleratedrunning to constant speed running.

Such control as described above is executed in a first control cycleafter the contact of the changing over switch 46 has been changed to anon-state. In case the automatic cruise mode control is executedcontinuously also in the following control cycle but the accelerationswitch 45 is not operated, the sequence advances via steps E101 and E110of FIG. 12 to step E128 to execute changing over switch control in sucha manner as described hereinabove.

Since contents of the control in the first control cycle after thecontact of the changing over switch 46 has been changed over to anon-state are the same as those of the control in the first control cycleafter the contact has been changed to an on-state during constant speedrunning of the vehicle, the relevant flags have the same values, andconsequently the changing over switch control is executed in a similarmanner. The sequence thus advances via steps E129 and E132 to step E133at which aimed speed control is executed in accordance with the flowchart shown at steps J101 to J116 of FIG. 16.

In the aimed speed control, it is judged at first at step J101 whetheror not the value of the flag I₈ is equal to 1. Since here the value ofthe flag I₈ has been changed to 0 at step E106 of FIG. 12 in the firstcontrol cycle after changing over of the changing over switch 46 to anon-state, the sequence advances from step J101 to step J102.

At step J102, it is judged whether or not the value of the flag I₁₁ isequal to 1. It is to be noted that the flag I₁₁ indicates, when itassumes a value equal to 1, that the present control cycle falls on atiming for opening or closing movement of the throttle value 31.

Since the present control cycle does not fall on a timing for opening orclosing movement of the throttle valve 31 when the value of the flag I₁₁is not equal to 1, the automatic cruise mode control in the presentcontrol cycle is completed immediately. To the contrary, in case thevalue of the flag I₁₁ is equal to 1, the present control cycle falls ona timing for opening or closing movement of the throttle valve 31, andaccordingly the sequence advances to step J103 to execute the aimedspeed control continuously.

In case the sequence advances to step J103, the actual speed VA read inat step A103 of FIG. 8(i) is substituted as a temporary value to theaimed speed VS for constant speed running. Thus, in preparation forcontrol after the running speed of the vehicle becomes substantiallyfixed, the aimed speed VS is updated in value for each control cyclewhich falls on a timing for opening or closing movement of the throttlevalve 31 until the running speed of the vehicle becomes substantiallyfixed in this manner.

Subsequently at step J104, it is judged whether or not the absolutevalue of the actual acceleration DVA into which DVA₆₅ or DVA₁₃₀ has beensubstituted as described hereinabove is smaller than the presetreference value Kα.

If it is judged at step J104 that the absolute value of the actualacceleration DVA is smaller than the reference value Kα because therunning speed of the vehicle has become substantially fixed and thedeceleration of the vehicle has approached 0 as a result of execution ofthe aimed speed control, the sequence advances to step J108 at which thevalue of the flag I₈ is changed to 0, whereafter the sequence advancesto step J109. To the contrary, in case the running speed has not yetbecome substantially fixed and the deceleration of the vehicle has notapproached 0, it is judged at step J104 that the absolute value of theactual acceleration DVA is not smaller than the reference value Kα, andthe sequence thus advances to step J105.

At step J105, it is judged whether or not the actual speed DVA isgreater than 0. Since here the vehicle has been in a decelerated runningcondition before the contact of the changing over switch 46 is changedto an on-state, the actual deceleration DVA has a negative value, andthe sequence thus advances to step J106.

At step J106, the value of the actual acceleration DVA added by thepreset correction amount ΔDV₂ is set to the aimed acceleration DVS,thereby completing the aimed speed control in the present control cycle.

After completion of such aimed speed control as described above, controlis executed subsequently at steps E123 to E127 of FIG. 12 in a similarmanner as in the various cases described hereinabove. Thus, the throttlevalve 31 is opened or closed to a throttle valve opening θ_(TH2)corresponding to the aimed acceleration DVS for each control cycle whichfalls on an opening/closing timing for the throttle valve 31.

As a result, the vehicle makes deceleration running at a negativeacceleration, that is, at a deceleration substantially equal to theaimed acceleration DVS.

Since the aimed acceleration DVS is a sum of the actual speed DVA in thecontrol cycle and the correction amount ΔDV₂, as such control isexecuted repetitively, the aimed acceleration DVS gradually approaches 0in negative value. Consequently, the deceleration of the vehicle alsoapproaches 0.

While the actual acceleration DVA approaches 0 in such a manner asdescribed above, if it is judged at step J104 of FIG. 16 that theabsolute value of the actual acceleration DVA is smaller than the presetreference value Kα, then the sequence advances via step J108 to stepJ109 as described hereinabove.

Control to be executed at step J109 and following steps J110 to J116 isthe same as the control executed at step J109 to J116 when a constantspeed running condition is entered as described above. Accordingly, inthe control cycle wherein the sequence advances from step J104 via stepJ108 and then step J109 to step J116, setting of a required aimedacceleration DVS is accomplished so that the vehicle may run at aconstant speed which coincides with the aimed speed VS set in value atstep J103.

To the contrary, in case the aimed speed changing switch 48 is changedover to the (+) side or the (-) side of FIG. 6, modification of the setvalue of the aimed speed VS is accomplished in response to such changingover.

Also after execution of such aimed speed control as described above,opening or closing movement of the throttle valve 31 is similarlyaccomplished in the control at steps E123 to E127 of FIG. 12, and thevehicle runs at a constant running speed substantially equal to theaimed speed VS.

It is to be noted that, in the following control cycle after a controlcycle in which the sequence advances from step J104 via step J108 tostep J109, since the value of the flag I₈ has been changed to 0 at stepJ108, the sequence advances, in aimed speed control, from step J101directly to step 109 so that such control as described above isexecuted.

Accordingly, in case, while the acceleration switch 46 is at theposition [a], at first the contact of the changing over switch 45 ischanged to an on-state to designate a decelerated running condition ofthe vehicle and then the contact is changed once to an off-statewhereafter the contact of the changing over switch 46 is changed to anon-state again while the vehicle still remains in a decelerated runningcondition as described hereinabove, the designation by the runningcondition designating section 3 of the control section 25 is changedover from decelerated running to constant speed running and thedecelerated running of the vehicle is stopped, and the vehicle willthereafter run maintaining a running speed which is substantially equalto the running speed at a point of time directly after the contact ofthe changing over switch 46 is changed to an on-state, that is, therunning speed when the designation is changed over to constant speedrunning.

As the automatic cruise mode control is executed in such a manner asdescribed so far, in case treadling of the brake pedal 28 is cancelledwhile the accelerator pedal 27 remains in a released condition or incase treadling of the accelerator pedal 27 is cancelled while the brakepedal 28 remains in a released condition, the vehicle makes constantspeed running while maintaining the running speed at a point of timedirectly after such cancelling of treadling.

Then, in case the acceleration switch 45 is changed over to any one ofthe positions [b] to [d] of FIG. 6 while the vehicle is in a constantspeed running condition or in case the contact of the changing overswitch 46 is changed to an on-state while the acceleration switch 45 isany one of the positions [b] to [d], the vehicle makes acceleratedrunning at an acceleration corresponding to the position [b], [c] or [d]of the acceleration switch 45, and then after the running speed of thevehicle reaches the final aimed speed, the vehicle makes constant speedrunning at a constant running speed substantially equal to the finalaimed speed. It is to be noted that, in case the contact of the changingover switch 46 is changed to an on-state to effect accelerated runningof the vehicle, the set value of the final aimed speed increases as theduration of the on-state of the changing over switch 46 increases.

To the contrary, in case the acceleration switch 45 is changed over tothe position [a] while the vehicle is in a constant speed runningcondition or in case the contact of the changing over switch 46 ischanged to an on-state while the acceleration switch 45 remains at theposition [a], the vehicle makes decelerated running, and after the finalaimed speed is reached, constant speed running of the vehicle isaccomplished at a constant running speed substantially equal to thefinal aimed speed. It is to be noted that, in case the contact of thechanging over switch 46 is changed to an on-state to effect suchdecelerated running of the vehicle as described above, the final aimedspeed decreases in set value as the duration of the on-state of thechanging over switch 46 increases.

Further, in case the contact of the changing over switch 46 is changedto an on-state again while the vehicle is either in an acceleratedrunning condition or in a decelerated running condition, the vehiclemakes constant speed running while maintaining a running speedsubstantially equal to the running speed at a point of time directlyafter the contact has been changed to an on-state.

For example, in case the acceleration switch 45 is changed over, duringaccelerated running of the vehicle with the acceleration switch 45positioned at the position [b], to the position [a], the vehicle makesconstant speed running while maintaining a running speed substantiallyequal to the running speed at a point of time directly after suchchanging over of the acceleration switch 45. To the contrary, in casethe aimed speed changing switch 48 is changed over to the (+) side orthe (-) side in FIG. 6 while the vehicle is in a constant speed runningcondition, the set value of the aimed speed for constant speed runningis increased or decreased in response to such changing over of the aimedspeed changing switch 48, and as the duration of such changing overincreases, the amount of increase or decrease of the set value of theaimed speed increases.

Subsequently, description will be given of throttle actuator failcontrol which allows torque adjustment to be executed within anallowable range when such failure takes place that the throttle actuator40 of the throttle valve pivoting section 26 is stopped at a certainopening due to disconnection or the like.

It is to be noted that the present control is a control to lower theoutput torque of the engine to a predetermined level in response to anengine speed or a treadled amount of the accelerator pedal 27 by 1rendering a suitable number of cylinders of the engine inoperative, 2adjusting the air fuel ratio of the engine to the lean side or 3delaying the ignition timing in angle of the engine, or by executingthose measures in a suitable combination. Such control is executed byway of the control section 25.

Particularly, the present engine includes the ignition speed controller(ISC) 53 interposed in a parallel relationship to the throttle valve 31in the bypass passage 52 provided for the intake air path 30. The ISC 53functions as a bypass passage opening/closing section which adjusts theamount of air to flow through the bypass passage 52, and also the ISC 53is utilized upon the throttle actuator fail control mentioned above.

In the following, the throttle actuator fail control will be describedwith reference to FIGS. 37(i) to 39.

Referring first to FIG. 37(i), an aimed throttle opening CPTG alreadyset is compared first at step T101 with an output value TPS of thethrottle opening sensor 41 (which corresponds to the control amountdetecting section 105a of the throttle actuator abnormal conditiondetecting means 105). Then, the sequence advances to step T102 at whichit is judged whether or not the aimed throttle opening CPTG issubstantially equal to the output value TPS.

If the aimed throttle opening CPTG is substantially equal to the outputvalue TPS and accordingly the throttle actuator 40 is not in failure,the sequence advances to step T107 at which a preset throttle actuatorfailure judgment time XTFAIL is placed into a throttle actuator failurejudgment counter CTFAIL. In the present instance, the throttle actuatorfailure judgment time XTFAIL is set to 1.0 second.

Then, the sequence advances to step T108 at which "0" is placed into atorque down instruction value TORDWN. The torque down instruction valueis a value corresponding to an amount to be reduced when the currentlyset torque is to be reduced. At the present step T108, since thethrottle actuator 40 remains in a normal condition and the currenttorque need not be reduced, the value "0" is used as the torque downinstruction value TORDWN.

On the other hand, if it is judged at step T102 that the aimed throttleopening CPTG is not substantially equal to the output value TPS of thethrottle opening sensor 41, in short, there is a difference by an amountgreater than a predetermined value between CPTG and TPS and consequentlyit is judged that the throttle actuator 40 is in failure, then thesequence advances to step T103.

At step T103, it is judged whether or not the fail condition hasoccurred successively for a predetermined period of time (that is, forthe throttle actuator failure judgment time XTFAIL). Here, the judgmentis whether or not the fail condition has occurred successively for 1.0second.

Such judgment is executed by decrementing the throttle actuator failurejudgment counter CTFAIL after each 10 ms in 10 ms timer interruptcontrol illustrated in FIG. 37(ii). Referring now to FIG. 37(ii), the 10ms timer interrupt control proceeds in the following manner. Inparticular, the throttle actuator failure judgment counter CTFAIL isfirst decremented by one at step T121, and then at subsequent step T122,it is judged whether or not the throttle actuator failure judgmentcounter CTFAIL is smaller than 0. Then, in case the counter CTFAIL issmaller than 0, it is reset to 0. Since the value of the counter CTFAILis decremented at step T121 until it is updated at step T107, if thepresent interrupt control is executed successively by a number of timescorresponding to the throttle actuator failure judgment time XTFAIL,then the counter CTFAIL becomes equal to 0. In other words, the judgmentat step T103 is equivalent to judgment whether or not the counter CTFAILis equal to 0 in the interrupt control. However, in case no failcondition has been entered, the value of the counter CTFAIL is normallyupdated to XTFAIL at step T107, and consequently, the counter CTFAIL isnot decremented to 0.

Referring back to FIG. 37(i), if the fail condition does not continue,at step T103, until the throttle actuator failure judgment time XTFAILelapses, the sequence advances to step T108, and consequently, torquedown control is not executed similarly as described above.

On the contrary, if the fail condition continues for the throttleactuator failure judgment time XTFAIL, then an abnormal conditiondetection signal will be developed from the abnormal condition detectionsignal developing section 105b of the throttle actuator abnormalcondition detecting means 105. Subsequently, the sequence advances tostep T104 at which the shift position detecting means (not shown) ischecked in order to judge whether or not the gear position is either inthe P (parking) range or in the N (neutral) range.

If the current gear position is in the P or N range, then the sequenceadvances to step T105 at which a torque down control is executed inresponse to an engine speed DRPM. In short, a torque down instructionvalue TORDWN is determined in accordance with a one-dimensional map#MTDWN1 using a current engine speed DRPM as a parameter.

Then at step T106, an instruction to reduce the torque is provided tothe control section 25 in accordance with the torque down instructionvalue TORDWN determined at step T105. Consequently, the control section25 executes 1 to render a suitable number of cylinders of the engineinoperative, 2 to adjust the air fuel ratio of the engine to the leanside or 3 to delay the ignition timing in angle of the engine orexecutes those measures in a suitable combination in order to lower theoutput torque of the engine to the predetermined level.

On the other hand, in case the gear position is neither in the P nor Nrange, in short, if the gear position is in the D (drive) range or insome other range, then the sequence advances to step T109 at which it isjudged at the air amount judging section 112a of the output reductioncontrol amount setting means 112 whether or not the value of the outputvalue TPS of the throttle opening sensor 41 subtracted from the aimedthrottle opening CPTG is greater than a predetermined value k₁.

Then, if it is judged at the air amount judging section 112a that thevalue of (CPTG-TPS) is greater than k₁, it is determined that the amountof air is insufficient, and consequently, an air amount shortage signalis developed, and then the sequence advances to step T110 at which theICS opening, in short, the control valve 53a of the ISC 53, is put intoa fully open condition by way of the opening/closing controlling section112b. On the other hand, if the value of (CPTG-TPS) is smaller than k₁at step T109, the air amount judging section 112a determines that theair amount is surplus and thus develops an air amount surplus signal.Then, the sequence advances to step T112 at which the ISC opening, inshort, the control valve 53 of the ISC 53, is put into a fully closedcondition by way of the opening/closing controlling section 112b.

From step T110 or step T112, the sequence subsequently advances to stepT111 at which torque reducing control is executed in response to theaccelerator position APS. In particular, a torque down instruction valueTORDWN is determined in accordance with a one-dimensional map #MTDWN2using the accelerator position APS as a parameter.

Then at subsequent step T106, a torque down instruction is provided tothe control section 25 in accordance with the torque down instructionvalue TORDWN determined at step T105. Consequently, the control section25 executes, in response to the accelerator position APS (that is, anaccelerator pedal treadled amount), 1 to render a suitable number of thecylinders of the engine inoperative, 2 to adjust the air fuel ratio ofthe engine to the lean side or 3 to delay the ignition timing in angleof the engine or executes those measures in a suitable combination inorder to lower the output torque of the engine to the predeterminedlevel.

As a result, even if the throttle actuator 40 fails, if the gearposition is either in the P range or in the N range, then the higher theengine speed, the more the set torque is reduced to lower the enginespeed to a predetermined level (for example, to an idling speed or so)and restrict a rise of the engine speed.

Meanwhile, if the gear position is in the D range or the like when thethrottle actuator 40 fails, the smaller the accelerator pedal treadledamount, the more the set torque is reduced in response to theaccelerator position APS. Accordingly, control of the output torque ofthe engine, in short, control of the engine speed, can be executed byadjusting the treadled amount of the accelerator pedal 27, andaccordingly, adjustment of the speed can be performed within a fixedrange.

Particularly, since such adjustment is performed within a range withinwhich the output torque is reduced by way of the one-dimensional map#MTDWN2, even if the upper limit of the output torque is restricted, thelower limit of the output torque is set such that it may not berestricted. Consequently, when the gear position is in the D range, ifthe treadled amount of the accelerator pedal 27 is reduced to 0, thenthe engine speed, in short, the engine output power, can be restricted.

While operation of engine control by the engine controlling system 1 isdescribed above, also control of a gear change of the automatictransmission 32 is executed by the automatic transmission controllingdevice together with the control by the engine controlling system.

Such speed change control (gear position changing control) of theautomatic transmission 32 will be described subsequently. In the case ofthe accelerator mode control by way of the accelerator pedal 15, as hasbeen the practice, shifting up or shifting down control is executed byway of the controller ELC in accordance with a map which uses anaccelerator treadled amount APS and an actual speed AV (the map isnormally stored in a RAM (not shown) of the automatic transmissioncontrolling means 107). However, upon power-on down-shifting(kick-down), this is permitted only after the changing rate (acceleratorpedal operating speed) DAVS of the accelerator pedal treadled amountexceeds a predetermined value.

However, when automatic cruise mode control wherein the acceleratorpedal 15 remains in a released condition is being executed, theaccelerator pedal treadled amount APS cannot be adopted as a controlparameter for the gear change control of the automatic transmission 32as in the prior art.

Thus, when such automatic cruise mode control is being executed, apseudo treadled amount SFTAPS is set, and speed change control of theautomatic transmission 32 is executed by way of the control ELC inaccordance with a map which employs such pseudo treadled amount SFTAPSand an actual speed AV as parameters.

It is to be noted that, while detailed construction of the automatictransmission controlling means 107 for controlling the automatictransmission 32 in accordance with a controlling condition of the enginecontrolling system 1 is not shown in the drawings, the automatictransmission controlling means 107 includes, in addition to aconventional transmission controlling means for controlling theautomatic transmission 32 to make a shifting up operation or a shiftingdown operation using an accelerator pedal treadled amount and an actualspeed as parameters, a speed comparing means for comparing an actualspeed with an aimed speed of the vehicle, an acceleration comparingmeans for comparing an actual acceleration with a preset referenceacceleration, a torque comparing means for calculating an actual outputtorque and comparing the calculated actual output torque with a maximumtorque at an engine speed at present, an engine speed comparing meansfor calculating an engine speed when the transmission is shifted downfrom a current gear position and comparing the calculated engine speedwith a predetermined value, and a gear change controlling means forsuitably providing a gear changing instruction to the automatictransmission 32 in accordance with information received from thosemeans.

The pseudo treadled amount SFTAPS is set to a predetermined value APS8when the vehicle is running at a constant speed or in a deceleratedcondition, but when the vehicle is running in an accelerated condition,the pseudo treadled amount SFTAPS is set in response to an aimedacceleration DVS set then.

Setting of the pseudo treadled amount upon accelerated running will bedescribed first. In this instance, the pseudo treadled amount SFTAPS andthe aimed acceleration DVS have such a relationship as, for example,shown in FIG. 30 and thus have a proportional relationship within afixed range. In FIG. 30, the pseudo treadled amount SFTAPS is indicatedby a unit of bits along the axis of abscissa while the aimedacceleration DVS is indicated by a unit of m/s² along the axis ofordinate.

Then, when the vehicle is making accelerated running, one of slowacceleration, intermediate acceleration and quick acceleration isdesignated as the running condition in response to a position of theautomatic cruise switch 18. Accordingly, if it is assumed that the slowacceleration is 1.5 m/s², the intermediate acceleration is 2.5 m/s² andthe quick acceleration is 3.5 m/s², then it can be seen from FIG. 30that the pseudo treadled amounts SFTAPS in slow acceleration,intermediate acceleration and quick acceleration are 83 bits, 117 bitsand 150 bits, respectively.

Such relational data of the pseudo treadled amount SFTAPS and the aimedacceleration DVS in various accelerated conditions are stored in the RAM(not shown) of the system so that they may be used in speed changecontrol of the automatic transmission 32 in automatic cruise modecontrol.

Further, when the vehicle is riding on an upward slope or on a downwardslope and the speed of the vehicle cannot be maintained only by enginecontrol, down-shift control of the automatic transmission 32 is executedby the automatic transmission controlling device so as to maintain thespeed of the vehicle. On the other hand, when rapid braking is carriedout by the brake pedal 28, down-shift control of the automatictransmission 32 is executed to render engine brake effective so as torapidly decelerate the vehicle.

At first, description is given of down-shift control for maintaining apredetermined speed of the vehicle upon riding on an upward slope or ona downward slope.

The down-shift control is executed as interrupt control for each 20milliseconds with such procedures as illustrated in FIGS. 28(i) and28(iii).

It is to be noted that FIGS. 28(i) and 28(ii) relate mainly todown-shift control upon riding on an upward slope while FIG. 28(iii)relates mainly to down-shift control upon riding on a downward slope.

Since such down-shift control is executed during constant speed runningcontrol in automatic cruise mode control, it is judged at first at stepP101 of FIG. 28(i) whether or not the current control mode is constantspeed running control in automatic cruise mode control. In case it isnot judged that the current control mode is constant speed runningcontrol in automatic cruise mode control, the sequence advances to stepP113 at which any special control for a down-shift is disabled. In otherwords, flags and so forth for preventing an up-shift are reset to cancelthe inhibition of an up-shift.

To the contrary, if it is judged at step P101 that the current controlmode is constant speed running control in automatic cruise mode control,then down-shift control will thereafter be executed under predeterminedconditions.

In short, in case a sufficient torque to maintain an aimed torque, forexample, upon riding on an upward slope cannot be obtained even if theengine is controlled so that the output thereof may be maximum, theactual speed VA will be lower than the aimed speed VS, and this isjudged at steps P102 and P103 by the car speed comparing means (notshown) of the automatic transmission controlling device.

In particular, it is judged at step P102 whether or not the actual speedVA is smaller than a fixed ratio to the aimed speed VS, and here, it isactually judged whether or not the speed VA of the vehicle is lower thana value equal to k₁ times the aimed speed VS. It is to be noted that k₁is a constant which satisfies k₁ <1.0 and is set, for example, to 0.95.Accordingly, if the vehicle speed VA is lower than 95% of the aimedspeed VS, then it is judged that the actual speed VA is excessively low.

Then at step P103, it is judged by what amount (i.e., by what km/h) theactual speed VA is lower than the aimed speed VS. Here, it is actuallyjudged whether or not the speed VA is lower by k₂ (km/h) than the aimedspeed VS. It is to be noted that k₂ is set here to 3.0 (km/h).Accordingly, in case the speed VA is lower than the aimed speed VS by anamount greater than 3.0 (km/h), it is judged at step P103 that theactual speed VA is excessively low.

If it is judged at step P104 that the actual speed VA is excessively lowin this manner, then it is judged at subsequent step P104 by theacceleration comparing means (not shown) of the automatic transmissioncontrolling device whether or not the vehicle is being accelerated(whether or not the speed of the vehicle is increasing). Here, it isactually judged whether or not the actual acceleration DVA is lower thana fixed acceleration value k₃ (m/s²), that is, DVA<k₃. It is to be notedthat k₃ may be set to zero or a positive value near zero, but here, thevalue of k₃ is set to 0.0 (m/s²) or 0.2 (m/s²).

If it is judged at step P104 that the vehicle is being accelerated, thenno gear change of the transmission is required because the actual speedis approaching the aimed speed. On the contrary, if it is not judgedthat the vehicle is being accelerated, then it is not expected that theactual speed may approach the aimed speed even if control of the engineis executed subsequently. Therefore, in such an instance, a gear changeof the transmission is required.

Here, the automatic transmission 32 has four gear positions including anoverdrive (fourth) gear position, and two types of down-shift controlfor a down-shift of the fourth to the third gear position and foranother down-shift of the third to the second gear position areexecuted. Accordingly, it is necessary to execute required control inaccordance with judgement to which gear position the automatictransmission is set at present.

Thus, it is judged at step P105 whether or not the current gear positionis the third gear position, and then it is judged at step P114 whetheror not the current gear position is the fourth gear position. In casethe current gear position is the third gear position, an enginerotational speed DRPM32 after carrying out of a down-shift of the thirdto the second gear position is calculated at step P106 in accordancewith a current engine rotational speed DRPM. On the other hand, if thecurrent gear position is the fourth gear position, an engine rotationalspeed DRPM43 after carrying out of a down-shift of the fourth to thethird gear position is calculated at step P115 in accordance with thecurrent engine rotational speed DRPM. It is to be noted that, sincenormally the third or fourth gear position is used during constant speedrunning control in automatic cruise mode control, the case wherein thecurrent gear position is the second gear position is not an object forthe down-shift control here, and in case the current gear position isthe first or second gear position, the sequence advances from step P114to step P117 of FIG. 28(ii).

After an engine rotational speed DRPM32 after carrying out of adown-shift is calculated at step P106, it is judged at subsequent stepP107 by the engine rotational speed comparing means (not shown) of theautomatic transmission controlling device whether or not the enginerotational speed DRPM32 is lower than a predetermined rotational speedXDRPM3 (for example, 3,500 rpm). Also after an engine rotational speedDRPM43 after carrying out of a down-shift is calculated at step P115, itis judged at subsequent step P116 whether or not the engine rotationalspeed DRPM43 is lower than another predetermined rotational speed XDRPM4(for example, 3,500 rpm).

Then, in case the engine rotational speed DRPM32 or DRPM43 is not lowerthan the predetermined rotational speed XDRPM3 or XDRPM4, no down-shiftcontrol should be performed, and therefore, the sequence advances tostep P117 of FIG. 28(ii). To the contrary, if the engine rotationalspeed DRPM32 or DRPM43 is lower than the predetermined rotational speedXDRPM3 or XDRPM4, then the sequence advances to step P108.

At step P108, a maximum torque TORMAX which can be produced at thecurrent engine rotational speed DRPM is determined from aone-dimensional map #MTORMX using the current engine rotational speedDRPM as a parameter.

Then at subsequent step P109, it is judged by the torque comparing means(not shown) of the automatic transmission controlling device whether ornot its current engine output torque TEM is within an available maximumtorque area. Such judgment involves comparison of the current engineoutput torque TEM with a value obtained by multiplying the maximumtorque TORMAX by a coefficient k₄ (here, k₄ =0.97), and if TEM is notequal to nor greater than TORMAXxk₄, then it is determined that theengine does not yet produce a maximum torque at present and it isexpected that the speed of the vehicle may be increased by enginecontrol. Therefore, the sequence advances to step P117 of FIG. 28(ii).To the contrary, if TEM is equal to or greater than TORMAXxk₄, then itis determined that the engine is substantially producing a maximumtorque, and the sequence thus advances to step P110 in order to increasethe speed of the vehicle by an increase of the torque by down-shiftcontrol.

At step P110, counting down of a first counter CDSAS1 for the judgementof a down-shift is started, that is, the first counter CDSAS1 isdecremented by one. Upon starting of such counting down, the value ofthe counter CDSAS1 is equal to a value XDSAS1 of a period for thedown-shift judgment due to such setting at step P117 of FIG. 28(ii) inthe preceding control cycle (such step P117 will be hereinafterdescribed). Here, the value XDSAS1 of the down-shift judgment period is50.

Then at subsequent step P111, it is judged whether or not the firstcounter CDSAS1 is equal to 0. However, in order for the counter CDSAS1to have a value equal to 0, the step P110 must be passed successivelyfor 50 cycles to execute counting down of the counter CDSAS1 by 50. Inshort, the counter CDSAS1 is reduced to 0 only after the followingconditions or requirements continue for a period of time of 50 controlcycles: that is, (1) the actual speed of the vehicle is excessively low;(2) the actual acceleration is lower than a predetermined value; (3) thecurrent gear position is either the third or the fourth gear position;(4) the engine is producing a substantially maximum torque at thecurrent engine rotational speed; and (5) the engine rotational speedafter carrying out of a down-shift does not exceed a predeterminedvalue. Since such down-shift control is interrupt control executed foreach 20 milliseconds, the period of 50 control cycles corresponds to onesecond.

Thus, if the counter CDSAS1 is not equal to 0 at step P111, then thesequence advances to step P118 of FIG. 28(ii) without carrying out adown-shift. To the contrary, if the counter CDSAS1 is equal to 0, thenthe sequence advances to step P112 at which a down-shift is carried outby the gear change controlling means (not shown) of the automatictransmission controlling device.

At step P112, a down-shift from the third to the second gear position orfrom the fourth to the third gear position is instructed while anup-shift is inhibited.

For the inhibition of an up-shaft, a flag FLG23 for the inhibition of anup-shift from the second to the third gear position and another flagFLG34 for the inhibition of an up-shift from the third to the fourthgear position may be used such that an up-shift may be enabled only whenthe up-shift inhibiting flag FLG23 or FLG34 is, for example, equal to 0.Accordingly, if a down-shift from the third to the second gear positionis to be carried out at step P112, then the up-shift inhibiting flagFLG23 is set to FLG23≠0, but if a down-shift from the fourth to thethird gear position is to be carried out at step P112, then the up-shiftinhibiting flag FLG34 is set to FLG34≠0.

After the down-shift is carried out in this manner, the value XDSAS1 ofthe preset down-shift judgment period is substituted as a value of thefirst down-shift judgement counter CDSAS1 at subsequent step P117 ofFIG. 28(ii).

It is to be noted that, in case it is judged at step P102, P103, P104,P107, P114, P116 or P109 that any one of the requirements for thecarrying out of a down-shift is not satisfied (i.e., in case there is noroute), the value of CDSAS1 is re-set to XDSAS1 at this step P117 in anycontrol cycle.

On the other hand, if the condition continues wherein all of therequirements for the carrying out of a down-shift are satisfied at stepsP102, P103, P104, P107, P114, P116 and P109, then the sequence advancesdirectly to step P118 bypassing the step P117 until the counter CDSAS1is reduced to 0 by counting down at step P110.

Referring to FIG. 28(ii), it is judged at step P118 whether or not anup-shift is inhibited. If an up-shift was inhibited at step P112 in thepresent or preceding control cycle and the inhibiting condition stillcontinues at step P118, then the sequence advances to step P119 tosubsequently execute control for the cancellation of the inhibitingcondition of an up-shift. To the contrary, if the inhibiting of anup-shift has been cancelled already, then the sequence advances to stepP141, thereby completing the down-shift control upon riding on an upwardslope.

At step P119, it is judged by the car speed comparing means whether ornot the current speed VA of the vehicle has sufficiently approached theaimed speed VS after the down-shift. Here, such judgment depends onwhether or not the current speed VA has approached the aimed speed VSuntil the difference between them is equal to or smaller than apredetermined value k₅ (=1.0 km/h), that is, VA≧VS-k₅. If the currentspeed VA is sufficiently near the aimed speed VS, then the sequenceadvances to step P120 to enter control for the cancellation of theinhibition of an up-shift in accordance with a current gear position. Tothe contrary, in case the current speed VA is not sufficiently near theaimed speed VS, the sequence advances to step P141, thereby completingthe down-shift control upon riding on an upward slope.

Since the flag FLG23 for the inhibition of an up-shift from the secondto the third gear position and the flag FLG34 for the inhibition of anup-shift from the third to the fourth gear position are provided, it isnecessary to judge which one of the inhibiting flags FLG23 and FLG34 iseffective at present in order to cancel the inhibiting condition of anup-shift. This can be detected from a current gear position, and if thetransmission assumes the second gear position at present, then theinhibiting flag FLG23 has a value other than 0, that is, FLG23≠0, but ifthe current gear position is the third gear position, then theinhibiting flag FLG34 is FLG34≠0.

Thus, it is judged at step P120 whether or not the current gear positionof the transmission is the second gear position, and then at step P128,it is judged whether or not the current gear position of thetransmission is the third gear position. If the current gear position isthe second gear position, then the sequence advances to step P121, butto the contrary if the current gear position is the third gear position,then the sequence advances to step P129. However, if the transmissionassumes any other gear position (either the first gear position or thefourth gear position), there is no necessity of cancelling theinhibition of an up-shift, and the sequence advances to step 141,thereby completing the down-shift control upon riding on an upwardslope.

After the sequence advances to step P121, an engine rotational speedDRPM23 for an instance when the gear position is changed from the secondto the third gear position is calculated. Then at subsequent step P122,a maximum torque TORMAX which can be produced from the engine after anup-shift at the engine rotational speed DRPM23 is determined inaccordance with the one-dimensional map #MTORMX using the enginerotational speed DRPM23 as a parameter. After then, the sequenceadvances to step P123 at which a drive shaft torque TORUP after carryingout of an up-shift is calculated in accordance with the maximum torqueTORMAX and the gear ratios at the third and second gear positions.

On the other hand, if the sequence advances to step P129, then an enginerotational speed DRPM34 for an instance when the gear position ischanged from the third to the fourth gear position is calculated. Thenat step P130, a maximum torque TORMAX which can be produced from theengine after carrying out of an up-shift at the engine rotational speedDRPM34 is determined in accordance with the one-dimensional map #MTORMXusing the engine rotational speed DRPM34 as a parameter. Subsequently,the sequence advances to step P140 at which a drive shaft torque TORUPafter carrying out of an up-shift is calculated in accordance with themaximum torque TORMAX and the gear ratios at the fourth and third gearpositions.

After a drive shaft torque TORUP after carrying out of an up-shift iscalculated at step P123 or step P140, the sequence advances to step P124at which it is judged by the torque comparing means whether or not thecurrent engine torque TEM is equal to or lower than the drive shafttorque TORUP calculated at step P123 or step P140. If the current enginetorque TEM is not equal to nor lower than TORUP, this is because theengine does not yet produce a sufficiently high torque, and theinhibiting condition of an up-shift should not be cancelled as yet. Inthis instance, the sequence advances to step P141. To the contrary, ifthe current engine torque TEM is equal to or lower than TORUP, then thetorque of the engine is sufficiently high for the engine to produce ahigher torque than the current drive shaft output torque after carryingout of an up-shift. In this instance, the sequence advances to step P125to enter a judgment period for the cancellation of inhibition of anup-shift.

At step P125, counting down of a first counter CUSAS1 for the judgmentof a down-shift is started, that is, the first counter CUSAS1 isdecremented by one. Upon starting of such counting down, the value ofthe counter CUSAS1 is equal to a value XUSAS1 of a period for thedown-shift judgment due to such setting at step P141 in the precedingcontrol cycle (such step P141 will be hereinafter described). Here, thevalue XUSAS1 of the down-shift judgment period is 5.

Then at subsequent step P126, it is judged whether or not the firstcounter CUSAS1 is equal to 0. However, in order for the counter CUSAS1to have a value equal to 0, the step P125 must be passed successivelyfor 5 cycles to execute counting down of the counter CUSAS1 by 5. Inshort, the counter CUSAS1 is reduced to 0 only after the followingconditions or requirements continue for a period of time of 5 controlcycles: that is, (1) an up-shift is inhibited; (2) the actual speed issufficiently near the aimed speed; (3) the current gear position iseither the second or the third gear position; and (4) the engine isproducing a sufficiently high output torque. Particularly as arequirement for production of a predetermined torque with certaintyafter carrying out of an up-shift, it is necessary that the engine beproducing a sufficiently high output torque and the condition wherein atorque higher than the current drive shaft output torque can be producedafter carrying out of an up-shift continue for a period of time longerthan a predetermined period of time (for 5 control cycles here). It isto be noted that, since the down-shift control is interrupt controlexecuted for each 20 milliseconds, the period of 5 control cyclescorresponds to 0.1 second.

Thus, if the counter CUSAS1 is not equal to 0 at step P126, thedown-shift control upon riding on an upward slope is completed and thesequence advances to step P142 of FIG. 28(iii). To the contrary, if thecounter CUSAS1 is equal to 0, then the sequence advances to step P127 atwhich flags and so forth for the inhibition of an up-shift are reset tocancel the inhibition of an up-shift by the gear change controllingmeans. It is to be noted that resetting of the up-shift inhibiting flagsincludes setting of the up-shift inhibiting flags FLG23 and FLG34 toFLG23=0 and FLG34=0, respectively.

After the inhibition of a down-shift is cancelled in this manner, thevalue XUSAS1 of the preset down-shift judgment period is substituted asa value of the first up-shift judgement counter CUSAS1 at subsequentstep P141.

It is to be noted that, in case it is judged at step P118, P119, P128 orP124 that there is no necessity of cancelling the inhibition of adown-shift (i.e., in case there is no route), the value of CUSAS1 isre-set to XUSAS1 at this step P141 in any control cycle.

On the other hand, if the condition continues wherein there is thenecessity of cancelling the inhibition of a down-shift at steps P118,P119, P128 and P124, then the sequence advances directly to step P142 ofFIG. 28(iii) bypassing the step P141 until the counter CUSAS1 is reducedto 0 by counting down at step P125.

Subsequently, down-shift control upon riding on a downward slope shownin FIG. 28(iii) will be described. The control for a downward slope isexecuted when the speed VA is so increased on a downward slope that,even if the engine output is controlled so as to present its minimumlevel, the speed VA may be exceed the aimed speed VS.

Referring to FIG. 28(iii), at first at steps P142 and P143, it is judgedby the speed ratio comparing means whether the current actual speed VAis restricted so that it may coincide with the aimed speed VS inautomatic cruise mode control designated by the automatic cruise switchor the like.

In particular, at step P142, it is judged whether or not the actualspeed VA has been reduced to a level equal to or lower than apredetermined ratio to the aimed speed VS, or more particularly, it isjudged whether or not the actual speed VA is higher than a valueobtained by multiplying the aimed speed VS by a constant k₆. It is to benoted that the value k₆ is 1.05 here.

In case it is judged at step P142 that the actual speed VA is higherthan a value of VS×k₆ and accordingly is excessively high, then thesequence advances to step P143 at which it is judged by what amount (inshort, by what km) the actual speed VA is higher than the aimed speedVS. Here, such judgment depends upon whether or not the differencebetween the actual speed VA and the aimed speed VS, that is, VA-VS, isgreater than a predetermined value k₇ (here, k₇ =3.0).

If the difference VA-VS is greater than the predetermined value k₇, itis determined that the speed of the vehicle is excessively high, and thesequence advances to step P144. At step P144, it is judged by theacceleration comparing means whether or not the actual acceleration DVAis higher than a predetermined acceleration value k₈ (m/s²), in short,DVA>k₈. It is to be noted that, while k₈ can be set to 0 or a negativevalue near 0, here it is set to 0.0 (m/s²) or -0.2 (m/s²).

If the actual acceleration DVA is higher than k₈, then it is determinedthat it is not expected that the actual speed VA can approach the aimedspeed VS by future control of the engine, and the sequence thus advancesto step P145.

To the contrary, if one of the judgments at steps P142, P143 and P144 isin the negative, it is determined that the speed VA is not excessivelyhigh or the actual speed VA can be caused to approach the aimed speed VSby future control of the engine. Consequently, down-shift control neednot be executed, and the sequence advances to step P153.

In the present embodiment, down-shift control is enabled only when thecurrent gear position is the fourth gear position, and accordingly, atstep P145, it is judged whether or not the current gear position of thetransmission 32 is the fourth gear position. In case the current gearposition is not the fourth gear position, down-shift control need not beexecuted, and the sequence advances to step P153.

To the contrary if the current gear position is the fourth gearposition, the sequence advances to step P146 at which an enginerotational speed DRPM43 when the gear position is changed from thefourth gear position to the third gear position is calculated. Then atsubsequent step P147, it is judged by the engine rotational speedcomparing means whether or not the engine rotational speed DRPM43 islower than a predetermined rotational speed XDRPM5 (for example, 3,500rpm).

Then, if the engine rotational speed DRPM43 is not smaller than thepredetermined rotational speed XDRPM3 at step P147, then down-shiftcontrol need not be executed, and the sequence advances to step P153. Tothe contrary, if the engine rotational speed DRPM43 is lower than thepredetermined rotational speed XDRPM5, then the sequence advances tostep P148.

At step P148, a minimum torque TORMIN which can be produced at thecurrent engine rotational speed is determined in accordance with aone-dimensional map #MTORMN using the current engine rotational speedDRPM as a parameter.

Then at step P149, it is judged by the torque comparing means whether ornot the current engine output torque TEM is within an available minimumtorque range. Such judgment depends on comparison of the current engineoutput torque TEM with a value obtained by multiplying the minimumtorque TORMIN by a coefficient k₉ (here, K₉ =1.03). For example, in casethe value of TEM is not equal to nor smaller than TORMINxk₉, the torquecan be reduced by engine control because a minimum torque is not reachedas yet, and the sequence advances to step P153. To the contrary, if thevalue of TEM is greater than TORMINxk₉, then this means that the engineis producing a substantially minimum torque, and the sequence thusadvances to step P150 in order to reduce the speed of the vehicle byreduction of a torque by down-shift control.

At step P150, counting down of a second counter CDSAS2 for the judgmentof a down-shift is started, that is, the second counter CDSAS2 isdecremented by one. Upon starting of such counting down, the value ofthe counter CDSAS2 is equal to a value XDSAS2 of a period for thedown-shift judgment due to such setting at step P153 in the precedingcontrol cycle (such step P153 will be hereinafter described). Here, thevalue XDSAS2 of the down-shift judgment period is 50.

Then at subsequent step P151, it is judged whether or not the secondcounter CDSAS2 is equal to 0. However, in order for the counter CDSAS2to have a value equal to 0, the step P150 must be passed successivelyfor 50 cycles to execute counting down of the counter CDSAS2 by 50. Inshort, the counter CDSAS2 is reduced to 0 only after the followingconditions or requirements continue for a period of time of 50 controlcycles: that is, (1) the actual speed of the vehicle is excessivelyhigh; (2) the actual acceleration is higher than a predetermined value;(3) the current gear position is the fourth gear position; (4) theengine is producing a substantially minimum torque at the current enginerotational speed; and (5) the engine rotational speed after carrying outof a down-shift does not exceed a predetermined value. Since suchdown-shift control is interrupt control executed for each 20milliseconds, the period of 50 control cycles corresponds to one second.

Thus, if the counter CDSAS2 is not equal to 0 at step P151, the sequenceadvances to step P154 without carrying out a down-shift. To thecontrary, if the counter CDSAS2 is reduced to 0, then the sequenceadvances to step P152 to carry out a down-shift.

At step P152, a down-shift from the fourth to the third gear position ofthe transmission is instructed while an up-shift is inhibited by thegear change controlling means. For the inhibition of an up-shift, theflag FLG34 for the inhibition of an up-shift from the third to thefourth gear position is set to FLG34≠0.

After a down-shift is carried out in this manner, the value XDSAS2 ofthe preset down-shift judgment period is substituted as a value of thesecond down-shift judgement counter CDSAS2 at subsequent step P153.

It is to be noted that, in case it is judged at step P142, P143, P144,P145, P147 or P149 that any one of the requirements for the carrying outof a down-shift is not satisfied (i.e., in case there is no route), thevalue of CDSAS2 is re-set to XDSAS2 at this step P153 in any controlcycle.

On the other hand, if the condition continues wherein all of therequirements for the carrying out of a down-shift are satisfied at stepsP142, P143, P144, P145, P147 and P149, then the sequence advancesdirectly to step P154 bypassing this step P153 until after the counterCDSAS2 is reduced to 0 by counting down at step P150.

At step P154, it is judged whether or not an up-shift is inhibited. Ifan up-shift was inhibited at step P152 in the present or precedingcontrol cycle and the inhibiting condition still continues at step P154,then the sequence advances to step P155 to subsequently execute controlfor the cancellation of the inhibiting condition of an up-shift. To thecontrary, if the inhibition of an up-shift has been cancelled already,then the sequence advances to step P164, thereby completing thedown-shift control upon riding on an upward slope.

At step P155, it is judged by the car speed comparing means whether ornot the current speed VA of the vehicle has sufficiently approached theaimed speed VS after the down-shift. Here, such judgment depends onwhether or not the current speed VA has approached the aimed speed VSuntil the difference between them is equal to or smaller than apredetermined value K₁₀ (=1.0 km/h), that is, VA-VS≧k₁₀. If the currentspeed VA is sufficiently near the aimed speed VS, the sequence advancesto step P156 to enter control for the cancellation of inhibition of anup-shift in accordance with a current gear position. To the contrary, incase the current speed VA is not sufficiently near the aimed speed VS,the sequence advances to step P164, thereby completing the down-shiftcontrol upon riding on an upward slope.

It is to be noted that, since the control stage of the cancellation ofinhibition of an up-shift at step P156 is provided by the flag FLG34 forthe inhibition of an up-shift from the third to the fourth gearposition, if the transmission assumes the third gear position atpresent, then the inhibiting flag FLG34 has a value other than 0, thatis, FLG34≠0.

Thus, it is judged at step P156 whether or not the current gear positionof the transmission is the third gear position, and then the currentgear position is the third gear position, then the sequence advances tostep P157. To the contrary, if the current gear position is not thethird gear position (i.e., the first, second or fourth gear position),there is no necessity of cancelling the inhibition of an up-shift, andthe sequence advances to step 164, thereby completing the down-shiftcontrol upon riding on an upward slope.

After the sequence advances to step P157, an engine rotational speedDRPM34 for an instance when the gear position is be changed from thethird to the fourth gear position is calculated. Then at subsequent stepP158, a minimum torque TORMIN which can be produced from the engineafter carrying out of an up-shift at the engine rotational speed DRPM34is determined in accordance with a one-dimensional map #MTORN using theengine rotational speed DRPM34 as a parameter. Then, the sequenceadvances to step P159 at which a drive shaft torque TORUP after carryingout of an up-shift is calculated in accordance with the minimum torqueTORMIN and the gear ratios at the fourth and third gear positions.

Then at subsequent step P160, it is judged by the torque comparing meanswhether or not the current engine torque TEM is equal to or higher thanthe drive shaft torque TORUP calculated at step P159. If the currentengine torque TEM is not equal to nor higher than TORUP, this is becausethe engine is still producing a substantially minimum torque, and theinhibiting condition of an up-shift should not be cancelled as yet. Thesequence thus advances to step P164. To the contrary, if the currentengine torque TEM is equal to or higher than TORUP, then it may bedetermined that the torque of the engine is so high on the lower limitside that the engine can produce a lower torque than the current driveshaft output torque after an up-shift. In this instance, the sequenceadvances to step P161 to enter a judging period for the cancellation ofinhibition of an up-shift.

At step P161, counting down of a second counter CUSAS2 for the judgmentof an up-shift is started, that is, the second counter CUSAS2 isdecremented by one. Upon starting of such counting down, the value ofthe counter CUSAS2 is equal to a value XUSAS2 of a period for thedown-shift judgment due to such setting at step P164 in the precedingcontrol cycle (such step P164 will be hereinafter described). Here, thevalue XUSAS2 of the down-shift judgment period is 5.

Then at subsequent step P162, it is judged whether or not the secondcounter CUSAS2 is equal to 0. However, in order for the counter CUSAS2to have a value equal to 0, the step P161 must be passed successivelyfor 5 cycles to execute counting down of the counter CUSAS2 by 5. Inshort, the counter CUSAS2 is reduced to 0 only after the followingconditions or requirements continue for a period of time of 5 controlcycles: that is, (1) an up-shift is inhibited; (2) the actual speed issufficiently near the aimed speed; (3) the current gear position is thethird gear position; and (4) the engine is producing a sufficiently highoutput torque on the lower limit side. Particularly as a requirement forthe production of a predetermined torque with certainty after anup-shift, it is necessary that the engine be producing a sufficientlyhigh output torque on the lower limit side and the condition wherein atorque lower than the current drive shaft output torque can be producedafter carrying out of an up-shift continue for a period of time longerthan a predetermined period of time (for 5 control cycles here). It isto be noted that, since the down-shift control is interrupt controlexecuted for each 20 milliseconds, the period of 5 control cyclescorresponds to 0.1 second.

Thus, if the counter CUSAS2 is not equal to 0 at step P162, then thepresent down-shift control upon riding on an upward slope is completedand a next control cycle is entered again after a predetermined intervalof time (20 ms). To the contrary, if the counter CUSAS2 is equal to 0,then the sequence advances to step P163 at which flags and so forth forthe inhibition of an up-shift are reset to cancel the inhibition of anup-shift by the gear change controlling means. It is to be noted thatsuch resetting of the up-shift inhibiting flags includes setting of theup-shift inhibiting flag FLG34 to 0.

After the inhibition of a down-shift is cancelled in this manner, thevalue XUSAS2 of the preset down-shift judgment period is substituted asa value of the second up-shift judgement counter CUSAS2 at subsequentstep P164.

It is to be noted that, in case it is determined at step P154, P155,P156 or P160 that there is no necessity of cancelling the inhibition ofa down-shift (i.e., in case there is no route), the value of CUSAS2 isre-set to XUSAS2 at this step P164 in any control cycle.

On the other hand, if the condition continues wherein there is thenecessity of cancelling the inhibition of a down-shift at steps P154,P155, P156 and P160, then the sequence advances to a next control cycleafter a predetermined interval of time (20 ms) bypassing the step P164until the counter CUSAS2 is reduced to 0 by counting down at step P161.

In this manner, when the vehicle is riding on an upward or downwardslope and it is impossible to maintain the speed of the vehicle only byengine control, down-shift control of the automatic transmission 32 isexecuted in addition to the engine control.

It is to be noted that, even in down-shift control upon riding on adownward slope, two kinds of down-shift control including down-shiftfrom the fourth to the third gear position and down-shift control fromthe third to the second gear position may alternatively be executedsimilarly as upon riding on an upward slope.

Such modified down-shift control is illustratively shown in FIGS. 28(iv)and 28(v) in which steps denoted by like reference characters involvelike contents of control to those of FIG. 28(iii).

Referring first to FIG. 28(iv), if it is not judged at step P144 thatthe vehicle is being decelerated, then it is not expected that theactual speed may approach an aimed speed even if control of the engineis executed in such condition. Accordingly, for the down-shift controlupon riding on a downward slope as mentioned above, a gear change of thetransmission is required.

Thus, it is judged at step P145 whether or not the current gear positionis the fourth gear position, and then it is judged at step P165 whetheror not the current gear position is the third gear position. If thecurrent gear position is the fourth gear position. then an enginerotational speed DRPM43 after carrying out of a down-shift from thefourth to the third gear position is calculated at step P146 inaccordance with the current engine rotational speed DRPM. But if thecurrent gear position is the third gear position, an engine rotationalspeed DRPM32 after carrying out of a down-shift from the third to thesecond gear position is calculated at step P166 in accordance with thecurrent engine rotational speed DRPM.

After an engine rotational speed DRPM43 after a down-shift is calculatedat step P146, it is judged at subsequent step P147 whether or not theengine rotational speed DRPM43 is lower than a predetermined rotationalspeed XDRMP5 (for example, 3,500 rpm). Also in case an engine rotationalspeed DRPM32 after carrying out of a down-shift is calculated at stepP166, it is judged at subsequent step P167 whether the engine rotationalspeed DRPM32 is lower than another predetermined rotational speed XDRPM6(for example, 3,500 rpm).

Then, in case the engine rotational speed DRPM43 or DRPM32 is equal toor higher than the predetermined rotational speed XDRPM5 or XDRPM6,down-shift control is not needed, and the sequence advances to step P153of FIG. 28(v). To the contrary, if the engine rotational speed DRPM43 orDRPM32 is lower than the predetermined rotational speed XDRPM5 orXDRPM6, then the sequence advances to step P148.

It is to be noted that, at step P152' after then, either down-shift ofthe gear position from the fourth to the third gear position ordown-shift from the third to the second gear position is instructedwhile an up-shift is inhibited. Such inhibition of an up-shift involvessetting of a flag FLG34 for the inhibition of an up-shift from the thirdto the fourth gear position to FLG34≠0 or setting of another flag FLG23for the inhibition of an up-shift from the second to the third gearposition to FLG23≠0.

In case two kinds of down-shift control for a down-shift from the fourthto the third gear position and another down-shift from the third to thesecond gear position are executed, also cancelling of the inhibition ofan up-shift is performed by changing the flag FLG23 for the inhibitionof an up-shift from the second to the third gear position or by changingthe flag FLG34 for the inhibition of an up-shift from the third to thefourth gear position. Accordingly, at first it is necessary to judgewhich one of the inhibiting flags is effective at present.

Thus, referring to FIG. 28(v), it is judged at step P156 whether or notthe current gear position of the transmission is the third gearposition, and then at step P168, it is judged whether or not the currentgear position of the transmission is the second gear position. Then, incase the current gear position is the third gear position, the sequenceadvances to step P157, but in case the current gear position is thesecond gear position, the sequence advances to step P169. In any othercase, that is, in case the current gear position is either the first orthe fourth gear position, there is no necessity of cancelling theinhibition of an up-shift, and the sequence thus advances to step P164,thereby completing the down-shift control of the present cycle.

In case the sequence advances to step P157, an engine rotational speedDRPM34 for an instance when the gear position is changed from the thirdto the fourth position is calculated at step P157. Then at subsequentstep P158, a minimum torque TORMIN which can be produced after carryingout of an up-shift at the engine rotational speed DRPM34 is determinedin accordance with the one-dimensional map #MTORMN using the enginerotational speed DRPM34 as a parameter. Subsequently, the sequenceadvances to step P159 at which a drive shaft torque TORUP after carryingout of an up-shift is calculated in accordance with the minimum torqueTORMIN and the gear ratios at the fourth and the third gear positions.

On the other hand, in case the sequence advances to step P169, an enginerotational speed DRPM23 for an instance when the gear position ischanged from the second to the third gear position is calculated at stepP169. Then at subsequent step P170, a minimum torque TORMIN which can beproduced after carrying out of an up-shift at the engine rotationalspeed DRPM23 is calculated in accordance with the one-dimensional map#MTORMN using the engine rotational speed DRPM23 as a parameter. Afterthen, the sequence advances to step P171 at which a drive shaft torqueTORUP after carrying out of an up-shift is calculated in accordance withthe minimum torque TORMIN and the gear ratios at the third and thesecond gear positions.

After a drive shaft torque TORUP after carrying out of an up-shift iscalculated at step P159 or step P171, the sequence advances to stepP160.

After then, control will proceed in a substantially similar manner as inthe control described hereinabove with reference to FIG. 28(iii).However, cancelling of the up-shift inhibiting flags and so forth atstep P163 is performed either by setting the up-shaft inhibiting flagFLG23 or or by setting the up-shift inhibiting flag FLG34 to 0.

As described above, where two kinds of down-shift control for the ridingon a downward slope are provided, for example, in accordance withcharacteristics of the engine of the vehicle, characteristics of theautomatic transmission 32 and so forth, a down-shift can be achievedfurther appropriately.

It is to be noted that, in case a gear change from the third to thesecond gear position is performed continuously after another gear changefrom the fourth to the third gear position is performed, it ispreferable to perform the later gear change from the third to the secondgear position after the running condition of the vehicle has beenstabilized directly after the earlier gear change (from the fourth tothe third gear position in this instance). In this case, the down-shiftjudgment counter CDSAS should be set to 150. Also when a gear changefrom the third to the fourth gear position is performed continuouslyafter another gear change from the second to the third gear position hasbeen carried out, it is preferable to execute the control in a similarmanner.

Subsequently, description will be given of down-shift control forcausing engine brake to act effectively to decelerate the vehiclerapidly.

Contents of the control include a main control illustrated in a flowchart of FIG. 29(i) and a 20 ms timer interrupt control illustrated inthe flow chart of FIG. 29(ii). Also the main control is executedcyclically for each predetermined interval of time. It is to be notedthat the down-shift control is executed when the gear position is set toa high speed gear position (third or fourth gear position) at which theeffect of engine brake is low.

The control illustrated in FIG. 29(ii) which is executed in 20 ms timerinterrupt to the main control will be first described. Referring to FIG.29(ii), in the control shown, the brake switch 16 is first checked atstep Q121 if it is on or off in order to judge whether or not thevehicle is being braked, and if the vehicle is not being braked, thevalue of a counter CDSBRK will not be decremented.

On the contrary, if the vehicle is being braked at step Q121, thesequence advances to step Q122 at which a count down amount DCRBRK isdetermined in accordance with a one-dimensional map #MDCRBK using acurrent acceleration DVA as a parameter.

Subsequently at step Q123, a braking time counter CDSBRK is decrementedby the count down amount DCRBRK.

Then at step Q124, it is judged whether or not the braking time countervalue CDSBRK is smaller than 0, and if the counter value CDSBRK issmaller than 0, the counter value CDSBRK is set to 0 at subsequent stepQ125.

Accordingly, if the count down amount DCRBRK is comparatively great withrespect to the braking time counter value CDSBRK, the counter valueCDSBRK is reduced to 0 after a comparatively short interval of time byway of a comparatively small number of control cycles, but on thecontrary if the count down value DCRBRK is comparatively small withrespect to the braking time counter value CDSBRK, the counter valueCDSBRK is reduced to 0 after a comparatively long interval of time byway of a comparatively large number of control cycles. It is to be notedthat the one-dimensional map #MDCRBK is such as, for example,illustrated in FIG. 30, and in accordance with the one-dimensional map#MDCRBK, a count down amount DCRBRK is set in response to a currentacceleration DVA (m/s²). Here, where the current acceleration DVA ishigher than -3 (m/s²), the count down amount DCRBRK is equal to 0, butwhere the current acceleration DVA is lower than -3 (m/s²), the countdown DCRBRK is provided in response to the magnitude of the accelerationDVA.

Accordingly, in slow braking wherein the deceleration is lower than 3m/s², no decrementing operation is executed, but in quick brakingwherein the deceleration is higher than 3 m/s², a count down amountDCRBRK is provided in accordance with the magnitude of a decelerationsuch that the quicker the braking, the greater the count down amountDCRBRK.

In short, if quick braking continues for a period of time longer than afixed period of time, then the count down amount is reduced to 0, andparticularly when the degree of braking is high, the count down amountDCRBRK is reduced to 0 in a correspondingly short period of time.

Here, the main control illustrated in FIG. 29(i) is described. First atstep Q101, the brake switch 16 is checked if it is on or off in order tojudge whether or not the vehicle is being braked, and if the vehicle isnot being braked, the braking time counter will be reset in accordancewith a current gear position. In short, the sequence advances to stepQ102 at which it is judged whether or not the current gear position isthe third gear position, and then if the current gear position is thethird gear position, the sequence advances to step Q103 at which thevalue CDSBRK of the braking time counter is reset to an initial value(third gear position braking time count amount) #XCBRK3. If the currentgear position is not the third gear position at step Q102, then thesequence advances to step Q104 at which it is judged whether or not thecurrent gear position is the fourth gear position, and if the currentgear position is the fourth gear position, the sequence advances to stepQ105 at which the value CDSBRK of the braking time counter is reset toanother initial value (fourth gear position braking time count amount)#XCBRK4. In case the current gear position is any other gear positionthan the third and fourth gear positions (that is, the first or secondgear position), resetting of the value CDSBRK of the braking timecounter is not effected.

On the other hand, if it is judged at step Q101 that the vehicle isbeing braked, the sequence advances to step Q106 at which it is judgedwhether or not the value CDSBRK of the braking time counter is equal to0.

The value CDSBRK of the braking time counter is successivelydecremented, while the vehicle is being braked, in the 20 ms timerinterrupt control illustrated in FIG. 29(ii). Thus, if it is judged atstep Q106 that the value CDSBRK of the counter is equal to 0, it isdetermined that the vehicle is being braked quickly and engine brakeshould be made effective, and when the current gear position is a highspeed gear position, down-shift control can be executed as describedbelow. On the contrary, if the counter value CDSBRK is not equal to 0 atstep Q106, then the present control cycle is completed, and if thecounter value CDSBRK is judged to be 0 in any following control cycle,then down-shift control can be executed in the control cycle.

In short, it is judged at step Q107 whether or not the current gearposition is the third gear position, and if the current gear position isthe third gear position, then the sequence advances to step Q108 atwhich an engine speed DRPM32 when the gear position is changed from thethird to the second gear position is calculated in a similar manner asdescribed hereinabove. Then at subsequent step Q109, it is judged by theengine speed comparing means 105 whether or not the engine speed DRPM32is lower than a predetermined speed XDRPM1 (for example, 5,500 rpm).

Then, if the engine speed DRPM32 is not lower than the predeterminedspeed XDRPM1, down-shift control will not be executed. In this instance,it is waited that the engine speed DRPM is decreased by deceleration bya treadling operation of the brake pedal 28 in any following controlcycle.

On the other hand, if the engine speed DRPM32 is lower than thepredetermined speed XDRPM11 at step Q109, then the sequence advances tostep Q110 in order to execute down-shift control.

At step Q110, an instruction to execute down-shifting of the gearposition from the third to the second gear position is developed fromthe gear position controlling means 106. Consequently, a down-shiftingoperation of the gear position from the third to the second gearposition is performed on the automatic transmission 32.

On the other hand, if it is judged at step Q107 that the current gearposition is not the third gear position and then it is judged atsubsequent step Q111 that the current gear position is the fourth gearposition, then the sequence advances to step Q112 at which an enginespeed DRPM43 when the gear position is changed from the fourth to thethird gear position is calculated in a similar manner as describedhereinabove. Then at subsequent step Q113, it is judged by the enginespeed comparing means 105 whether or not the engine speed DRPM43 islower than a predetermined speed XDRPM2 (for example, 5,500 rpm).

Then, if the engine speed DRPM43 is not lower than the predeterminedspeed XDRPM2, down-shift control will not be executed. In this instance,it is waited that the engine speed DRPM is lowered by deceleration by atreadling operation of the brake pedal 28 in any following controlcycle.

On the contrary, if the engine speed DRPM43 is lower than thepredetermined speed XDRPM2 at step Q113, the sequence advances to stepQ114 at which the value CDSBRK of the braking time counter is reset tothe initial value (third gear position braking time count amount)#XCBRK3 so that, after down-shift control of the gear position from thefourth to the third gear position is executed in the present controlcycle, another down-shift control of the gear position from the third tothe second gear position may be executed in any following control cycle.

Then, at subsequent step Q115, an instruction to execute down-shiftcontrol of the gear position from the fourth to the third gear positionis developed from the gear position controlling means 106, and adown-shifting operation of the gear position from the fourth to thethird gear position is performed on the automatic transmission 32.

In this manner, upon quick braking wherein the degree of deceleration ishigher than a fixed level, a down-shifting operation from the third tothe second gear position or from the fourth to the third gear positionis performed so that deceleration of the vehicle may be prompted whileengine brake is acting effectively. Further, the time until adown-shifting operation is performed after starting of braking isdifferent in accordance with a degree of quick braking, and the quickerthe braking, the faster the down-shifting operation.

Description of the contents of the control of the automatic transmission32 is thus completed. Subsequently, control for reducing a speed changeshock upon up-shifting operation of the automatic transmission 32 willbe described.

Normally, when an up shifting operation of the automatic transmission 32is performed, some variation takes place in torque of the output shaftof the automatic transmission 32, which may result in a speed changestock. Particularly when a speed changing operation comes to an end, agreat speed change shock is caused by rapid reduction of the torque ofthe output shaft of the automatic transmission 32. Thus, for a period oftime from starting to ending of an up-shifting operation, the throttleopening of the engine 13 is temporarily reduced by the engine controlsection 25 in accordance with information detected by the gear positiondetecting section 23 in order to restrict a possible variation of thetorque of the output shaft of the automatic transmission 32 thereby toreduce a shock which likely takes place upon speed changing operation.

The speed change shock reducing control is executed in such a manner asillustrated in the flow charts shown in FIGS. 31(i) to 31(iv) andincludes a shock reducing control illustrated in FIG. 31(i) mainly forthe up-shifting operation from the first to the second gear position,another shock reducing control illustrated in FIG. 31(ii) mainly for theup-shifting operation from the second to the third gear position, and afurther shock reducing control illustrated in FIG. 31(iii) mainly forthe up-shifting operation from the third to the fourth gear position. Itis to be noted that a time count value obtained in 5 ms interruptcontrol illustrated in FIG. 31(iv) is used in those shock reducingcontrols.

Meanwhile, in the up-shifting shock reducing control, a condition ofrotation of the kick-down drum is detected by the gear positiondetecting means 23 in the form of a kick-down drum rotating conditiondetecting means, and a timing of starting of a closing movement of thethrottle valve 31 is determined in response to the rotation condition ofthe kick-down drum thus detected.

In the present control, it is first judged, at step S101 shown in FIG.31(i), whether or not a speed changing operation is proceeding. Then, ifno speed changing operation is proceeding, the present shock reducingcontrol is completed, but on the contrary if a speed changing operationis proceeding, the sequence advances to step S102 at which it is judgedwhether or not an up-shifting instruction is effective at present.

If no up-shifting instruction is effective, then the present up-shiftingshock reducing control is completed, but on the contrary if anup-shifting instruction is effective, the sequence advances to stepS103.

At step S103, it is judged whether or not the up-shifting instruction isan up-shifting instruction from the first to the second gear position.If the current up-shifting instruction is not an up-shifting instructionfrom the first to the second gear position, then this means that it isanother up-shifting instruction, and the sequence thus advances to stepS131 shown in FIG. 31(ii).

On the other hand, if the current up-shifting instruction is anup-shifting instruction from the first to the second gear position, thena shock reducing control for the up-shifting operation from the first tothe second gear position corresponding to such up-shifting operationwill be executed.

In short, the sequence advances to step S104 at which it is judgedwhether or not the kick-down switch (K/DSW) is in an off-state atpresent. In case the kick-down switch K/DSW is not in an off-state, thepresent up-shifting shock reducing control is completed, but if it is inan off-state, the sequence advances to step S105.

At step S105, it is judged whether or not the kick-down switch K/DSW ischanged over from an on-state to an off-state in the present controlcycle and is now in an off-state. In short, it is judged whether or nota kick-down operation has been performed until the preceding controlcycle by a treadling operation of the accelerator pedal 27 and thetreadled amount of the accelerator pedal 27 is decreased in the presentcontrol cycle so as to achieve up-shift to the second gear positionagain.

If the kick-down switch K/DSW is changed over to an off-state in thepresent control cycle, the sequence advances to step S106, but otherwiseif the kick-down switch K/DSW is not changed over in the present controlcycle, the sequence advances to step S109.

At step S106, a current engine output torque TEM is set as a speedchange base torque SFTEM. The speed change base torque SFTEM denotes atorque upon starting of a gear position changing instruction (anup-shifting operation here).

Then at subsequent step S107, a throttle closing timing (interval oftime till starting of a closing movement of the throttle valve) TSHUTwith reference to a point of time of turning off of the K/D (kick-down)switch is determined in accordance with a one-dimensional map #MSHT12(not shown) using a current value PPG8 of the throttle opening O_(th).The value of TSHUT is set such that it decreases as the current throttleopening PPG8 increases.

It is to be noted that, since the magnitude of a hydraulic pressure tobrake the kick-down drum (K/D) drum is mapped with respect to thethrottle opening O_(th) by the controlling section of the automatictransmission 32, the hydraulic pressure to brake the K/D drum iscontrolled suitably in response to a throttle opening O_(th).Accordingly, also a period of time till the rotational speed of the K/Ddrum begins to decrease after turning off of the K/D switch isdetermined in response to a throttle opening O_(th) (PPG8).

Then at subsequent step S108, the value of a timer CSFT is reset to 0,and a counting operation of the timer CSFT is started.

Such counting operation of the timer CSFT is executed in accordance withsuch 5 ms timer interrupt control as illustrated in FIG. 31(iv). Thus,referring to FIG. 31(iv), it is judged first at step S121 whether or notthe timer CSFT is in a stopping condition of FF_(H), and if it is in astopping condition of FF_(H), then no counting operation is performedsubsequently, but on the contrary if the timer CSFT is not in a stoppingcondition of FF_(H), a counting operation should be performed.Accordingly, after the value of the timer CSFT is reset to 0 at stepS108, a counting operation at step S122 is started, and the value of thetimer CSFT is incremented for each 5 ms.

On the other hand, if the kick-down switch K/DSW was changed over to anoff-state in any preceding control cycle, the sequence advances fromstep S105 to step S109 at which it is judged whether or not the value ofthe timer CSFT reaches the throttle closing timing TSHUT (CSFT TSHUT).Then, if CSFT does not reach TSHUT, then the sequence advances to stepS110, but if CSFT reaches TSHUT, the sequence advances to step S113.

It is to be noted that, after a counting operation of the timer CSFT isstarted at step S122 shown in FIG. 31(iv) after changing over of thekick-down switch K/DSW to an off-state, in any control cycle until thevalue of the timer CSFT reaches the throttle closing timing TSHUT whilesuch off-state continues, the sequence advances from step S109 to stepS110 at which a control of closing the throttle valve 31 a little isexecuted as a preceding stage to execution of a control of formallyclosing the throttle valve 31. Then, after the value of the timer CSFTreaches the throttle closing timing TSHUT, the sequence advances to stepS113 in order to execute a control of formally closing the throttlevalve 31.

At step S110 to which the sequence advances from step S109, a kick-downdrum speed KDRPM1 is calculated from an output shaft speed VSRPM2. Thekick-down drum speed KDRPM1 represents a rotational speed of thekick-down drum upon a speed changing operation and can be calculated bymultiplying a predetermined gear ratio to a value of VSRPM2. It is to benoted that, at the present step S110, a current kick-down drum speed maybe detected (or calculated) and used as a value of the rotational speedKDRPM1.

Subsequently at step S111, a throttle returning kick-down drum speedRTNRPM is determined from a one-dimensional map #MRTN12 shown in FIG.34(i) using the kick-down drum speed KDRPM1 as a parameter. It is to benoted that the throttle returning kick-down drum speed RTNRPM is arotational speed of the kick-down drum when the throttle valve 31 is tobe returned to its original position, and within a fixed range of thevalue of the speed KDRPM1, it increases in proportion to the speedKDRPM1.

The reason why the throttle returning kick-down drum speed RTNRPM is setin this manner is that, for example, when the kick-down drum speedKDRPM1 is high at an initial stage, if the set value of the throttlereturning kick-down drum speed RTNRPM is not high, then a shock reducingoperation by a closing movement of the throttle valve 31 will be delayedwith respect to a shifting up operation which requires a substantiallyfixed period of time.

Then, at subsequent step S112, the speed change base torque SFTEMobtained at step S106 is placed into the aimed engine output torque TOM,and then the sequence advances to step S117. The reason why the speedchange base torque SFTEM is used as the aimed engine output torque TOMin this manner is that the throttle valve 31 can be closed a littleconsequently and when the throttle valve 31 is to be closed formally,the closing movement can be completed rapidly to raise the controllingspeed because the opening upon starting of such closing movement issmall. It is to be noted that, even if the throttle valve 31 is closedto a throttle opening at which the speed change base torque SFTEM isobtained, no variation will take place in output torque and there is notrouble against stabilized control of torque.

On the other hand, if it is judged at step S109 that the timer CSFTreaches the throttle closing timing TSHUT, the sequence advances to stepS113 at which it is judged where or not the current kick-down drum speedKDRPM has reduced to a value lower than the throttle returning kick-downdrum speed RTNRPM.

After an up-shifting operation from the first to the second gearposition is started, the kick-down drum speed KDRPM begins to decreasein response to a closing movement of the throttle valve 31. However,after the value KDRPM is decreased to a value lower than the throttlereturning kick-down drum speed RTNRPM, the up-shifting shock reducingcontrol of the present control cycle is completed, and the throttleopening θ_(TH) is set to an opening instructed by way of the acceleratoror the like (an opening normally instructed). On the other hand, if thekick-down drum speed KDRPM has not been decreased to a value lower thanthe throttle returning kick-down drum speed RTNRPM, then it isdetermined that the decrease of the kick-down drum speed KDRPM till thenis not yet sufficient, and the sequence advances to step S114 and thento step S115 in order to set correction torque values T_(C1) and T_(C2)for the determination of temporary amounts of closing movement of thethrottle valve 31.

In particular, at step S114, a correction torque T_(C1) is determinedfrom a one-dimensional map MTIM12 shown in FIG. 35 using a differencebetween a time after starting of a closing movement of the throttlevalve, in short, the speed change timer CSFT, and the throttle closingtiming TSHUT, that is, CSFT-TSHUT as a parameter. The correction torqueT_(C1) is significant of so-called "seasoning to a torque variation" toimprove the running feeling of the vehicle upon changing of the torqueof the vehicle.

At subsequent step S115, another correction torque T_(C2) is determinedfrom another one-dimensional map #MRPM12 shown in FIG. 36 using thekick-down drum speed KDRPM1 before the closing movement of the throttlevalve as a parameter. It is to be noted that, while the correctiontorque T_(C2) is set such that, as in the case of the one-dimensionalmap #MRPM12 shown in FIG. 36, the higher the kick-down drum speed KDRPM1before closing movement of the throttle valve, the higher the correctiontorque T_(C2), this is because it is forecast that, when the kick-downdrum speed KDRPM1 is high, the engine is rotating at a high speed and isin a high output power condition as much, and in order to restrict apossible shock upon changing of the gear position, in case the speedKDRPM1 is high, then there is no effect if the correction torque T_(C2)is not high as much.

Further at step S116, a value obtained by substraction of the correctiontorque values T_(C1) and T_(C2) from the speed change base torque SFTEM,that is, SFTEM-TC₂₁ -T_(C2), is placed into the aimed engine outputtorque TOM, and then the sequence advances to step S117.

At step S117, an aimed throttle opening CPTG is determined from thetwo-dimensional map #ACTRTH using the current engine speed DRPM and theaimed torque TOM as parameters. At subsequent step S118, a maximumthrottle opening THMAX is determined from a one-dimensional map #THCLPusing the current engine speed DRPM as a parameter. The maximum throttleopening THMAX is such an opening of the throttle valve a greater openingthan which will provide no change in torque, and is a value determinedin accordance with an engine speed.

Then at step S119, it is judged whether or not the maximum throttleopening THMAX is smaller than the aimed throttle opening CPTG, and ifTHMAX is not smaller than CPTG, the aimed throttle opening CPTGdetermined at step S117 is adopted, thereby completing the up-shiftingshock reducing control of the present control cycle. However, on thecontrary if THMAX is smaller than CPTG, then the sequence advances tostep S120 at which the maximum throttle opening THMAX is set to theaimed throttle opening CPTG, thereby completing the up-shifting shockreducing control of the present control cycle.

Here, variations of the throttle valve 31, timer CSFT, kick-down drumspeed, condition of the kick-down switch and torque of the output shaftof the torque converter 32 in up-shifting shock reducing control fromthe first to the second gear position will be described with referenceto the time charts of FIGS. 32(i) to 32(iii).

If the kick-down switch K/DSW is changed over from an on-state to anoff-state, in short, an up-shifting instruction from the first to thesecond gear position is developed, at a point of time t_(A) (refer toFIG. 32(ii)), then a speed change base torque SFTEM is first stored, anda throttle closing timing TSHUT is determined and the counter CSFT isreset to 0 to start a counting operation thereof (refer to FIG. 32(i)).

Then, in a subsequent next control cycle, the throttle valve 31 isclosed a little using the speed change base torque SFTEM as an aimedtorque (refer to FIG. 32(i)).

By performing such preparatory operation, a closing movement when thethrottle valve 31 is to be closed formally can be completed rapidlyafter starting of such closing movement, and the controlling speed canbe increased. Even if such preparatory operation is performed, there isno trouble against stabilized control of torque.

Then, after the volume of the timer CSFT reaches the throttle closingtiming TSHUT at a shifting operation starting point of time t_(B), thethrottle valve 31 is closed formally (refer to FIG. 32(i)). Togetherwith such closing movement, also the kick-down drum speed KDRPM beginsto decrease.

Then at a further point of time t_(C) at which the current kick-downdrum speed KDRPM is reduced to the throttle returning kick-down drumspeed RTNRPM while the throttle valve 31 is held in the closedcondition, the opening of the throttle valve 31 is placed under normalopening control in accordance with an opening instructed by way of theaccelerator or the like. Consequently, the throttle opening θ_(TH) isreturned to its initial opening.

As a result, the variation of the torque of the output shaft of theautomatic transmission 32 is reduced to a very low level comparing withan alternative case wherein such shock reducing control is not executedas seen in FIG. 32(iii). Particularly, rapid reduction of the torque ofthe output shaft of the automatic transmission 32 upon completion of aspeed changing operation is moderated. Consequently, a speed changeshock is reduced.

By the way, if it is judged at step S103 of FIG. 31(i) that theup-shifting instruction is not an up-shifting instruction from the firstto the second gear position and then it is judged at step S131 to whichthe sequence advances from step S103 that the up-shifting instruction isan up-shifting operation from the second to the third gear position,then a shock reducing control for the up-shift from the second to thethird gear position is executed subsequently.

In this instance, the sequence first advances to step S132 at which itis judged whether or not a speed changing operation was proceeding inthe preceding control cycle, and if a speed changing operation isentered at first in the present control cycle, the sequence advances tostep S133, but if a speed changing operation has been proceeding fromthe preceding control cycle, the sequence advances to step S136.

At step S133, a current engine output torque TEM is set as a speedchange base torque SFTEM similarly as at step S106 of FIG. 31(i).

Then at subsequent step S134, a throttle closing timing TSHUT isdetermined in accordance with a one-dimensional map #MSHT23 (not shown)using a current throttle opening PPG8 similarly as at step S107 of FIG.31(i).

Then at step S135, the value of a timer CSFT is reset to 0 and acounting operation of the timer CSFT is started similarly as at stepS108 of FIG. 31(i).

Also such counting operation of the timer CSFT is executed in such 5 mstimer interrupt control as illustrated in FIG. 31(iv).

On the other hand, in case it is determined at step S132 that a speedchanging operation has been proceeding from the preceding control cycleand consequently the sequence advances to step S136, it is judged atstep S136 whether or not the value of the timer CSFT reaches thethrottle closing timing TSHUT. Then, if CSFT reaches TSHUT, the sequenceadvances to step S137, but if CSFT does not reach TSHUT, the sequenceadvances to step S140.

At step S137, a kick-down drum speed KDRPM2 is calculated from an outputshaft speed VSRPM2 similarly as at step S110 of FIG. 31(i). Thekick-down drum speed KDRPM2 represents a rotational speed of thekick-down drum upon a speed changing operation and can be calculated bymultiplying a predetermined gear ratio to a value of VSRPM2. It is to benoted that, also here at step S137, a current kick-down drum speed maybe detected and used as a value of the rotational speed KDRPM2.

Subsequently, at step S138, a throttle returning kick-down drum speedRTNRPM is determined in accordance with a one-dimensional map #MRTN23shown in FIG. 34(ii) using the kick-down drum speed KDRPM2 as aparameter similarly as at step S111 of FIG. 31(i).

Then, at subsequent step S139, the speed change base torque SFTEM isplaced into the aimed engine output torque TOM, and then the sequenceadvances to step S117 of FIG. 31(i).

On the other hand, if it is judged at step S136 that the value of thetime CSFT reaches the throttle closing timing TSHUT and consequently thesequence advances to step S140, it is judged at step S140 whether or notthe current kick-down drum speed KDRPM has increased to the throttlereturning kick-down drum speed RTNRPM.

After an up-shifting operation from the second to the third gearposition is started, the kick-down drum speed KDRPM begins to rise inresponse to a closing movement of the throttle valve 31. However, if thevalue KDRPM is increased to the, throttle returning kick-down drum speedRTNRPM, the up-shifting shock reducing control of the present controlcycle is completed, and the throttle opening θ_(TH) is set to an openinginstructed by way of the accelerator or the like (an opening normallyinstructed).

On the other hand, if the kick-down drum speed KDRPM has not beenincreased to the throttle returning kick-down drum speed RTNRPM, thenS190, it is determined that the increase of the kick-down drum speedKDRPM till then is not yet sufficient, and the sequence advances to stepS141 and then to step S142 in order to set correction torque valuesT_(c1) and T_(C2) for the determination of temporary amounts of closingmovement of the throttle valve 31.

In particular, at step S141, a correction torque T_(C1) is determinedfrom a one-dimensional map #MTIM23shown in FIG. 35 using a differencebetween a time after starting of a closing movement of the throttlevalve, in short, the speed change timer CSFT and the throttle closingtiming TSHUT, that is, CSFT-TSHUT, as a parameter. The correction torqueT_(C1) is significant to improve the running feeling of the vehicle uponchanging of the torque of the vehicle similarly as in the case describedhereinabove.

At subsequent step S142, another correction torque T_(C2) is determinedfrom another one-dimensional map #MRPM23 shown in FIG. 36 using thekick-down drum speed KDRPM2 before the closing movement of the throttlevalve as a parameter. It is to be noted that the reason why thecorrection torque T_(C2) is set such that, as in the case of theone-dimensional map #MRPM23 shown in FIG. 36, the higher the kick-downdrum speed KDRPM2 before closing movement of the throttle valve, thehigher the correction torque T_(C2), is that it is intended to restricta shock upon changing with certainty similarly as described hereinabove.

Further at step S143, a value obtained by subtraction of the correctiontorque values T_(C1) and T_(C2) from the speed change base torque SFTEM,that is, SFTEM-TC₂₁ -T_(C2), is placed into the aimed engine outputtorque TOM, and then the sequence advances to step S117.

Then, an aimed throttle opening CPTG is determined at step S117, andthen at step S118, a maximum throttle opening THMAX is determined usingthe current engine speed DRPM as a parameter, similarly as describedhereinabove.

Then at step S119, it is judged whether or not the maximum throttleopening THMAX is smaller than the aimed throttle opening CPTG, and ifTHMAX is not smaller than CPTG, the aimed throttle opening CPTGdetermined at step S117 is adopted, but on the contrary if THMAX issmaller than CPTG, the sequence advances to step S120 at which themaximum throttle opening THMAX is set to the aimed throttle openingCPTG, thereby completing the up-shifting shock reducing control of thepresent control cycle.

Variations of the throttle valve 31, timer CSFT, kick-down drum speedand torque of the output shaft of the torque converter 32 in shockreducing control upon such up-shift from the second to the third gearposition will be described subsequently with reference to the timecharts of FIGS. 33(i) to 33(iii).

If an up-shifting instruction from the second to the third gear positionis developed at a point of time t_(A), then a speed change base torqueSFTEM is first stored, and a throttle closing timing TSHUT is determinedand the counter CSFT is reset to 0 to start a counting operationthereof.

Then, in a subsequent next control cycle, the throttle valve 31 isclosed a little using the speed change base torque SFTEM as an aimedtorque. As a result, a closing movement of the throttle valve 31 for theabsorption of a shock can be increased similarly as describedhereinabove.

Then, if the value of the timer CSFT reaches the throttle closing timingTSHUT at a shifting operation starting point of time t_(B), the throttlevalve 31 is closed formally, and also the kick-down drum speed KDRPMbegins to decrease.

Then at a further point of time t_(c) at which the current kick-downdrum speed KDRPM is increased to the throttle returning kick-down drumspeed RTNRPM while the throttle valve 31 is held in the closedcondition, the opening of the throttle valve 31 is placed under normalopening control in accordance with an opening instructed by way of theaccelerator or the like. Consequently, the throttle opening θ_(TH) isreturned to its initial opening.

As a result, the variation of the torque of the output shaft of theautomatic transmission 32, particularly rapid reduction of the torque ofthe output shaft of the automatic transmission 32 upon completion of aspeed changing operation, is moderated, and a speed change shock isreduced.

Subsequently, description will be given of shock reducing control uponup-shifting from the third to the fourth gear position illustrated inFIG. 31(ii).

The present control is executed when it is judged at step S103 of FIG.31(i) that the up-shifting instruction is not an up-shifting instructionfrom the first to the second gear position and then it is judged at stepS131 to which the sequence advances from step S103 that the up-shiftinginstruction is not an up-shifting instruction from the second to thethird gear position, whereafter it is judged at step 151 to which thesequence advances from step 131 that the up-shifting instruction is anup-shifting instruction from the third to the fourth gear position.

In this instance, the sequence first advances to step S152 at which itis judged whether or not a speed changing operation was proceeding alsoin the preceding control cycle, and in case a speed changing operationis started in the present control cycle, the sequence advances to stepS156, but if a speed changing operation was proceeding in the precedingcontrol cycle, the sequence advances to step S153.

At step S153, the speed change base torque SFTEM is set to the currentengine output torque TEM similarly as at step S106 of FIG. 31(i).

Then, at subsequent step S154, a throttle closing timing TSHUT isdetermined in accordance with a one-dimensional map #MSHT34 (not shown)using a current throttle opening PPG8 similarly as at step S107 of FIG.31(i).

Subsequently at step S155, the value of the timer CSFT is reset to startcounting of the timer CSFT similarly as at step S108 of FIG. 31(i).

Also such counting of the timer CSFT is executed in such 5 ms timerinterrupt control as illustrated in FIG. 31(iv).

On the other hand, if it is determined at step S152 that a speedchanging operation was proceeding in the preceding control cycle andconsequently the sequence advances to step S156, it is judged at stepS156 whether or not the value of the timer CSFT reaches the throttleclosing timing TSHUT. If CSFT reaches TSHUT, then the sequence advancesto step S157, but if CSFT does not reach TSHUT, then the sequenceadvances to step S140.

In case the sequence advances to step S157, a kick-down drum speedKDRPM3 is calculated at step S157 from an output shaft speed VSRPM2similarly as at step S110 of FIG. 31(i). The kick-down drum speed KDRPM3represents a rotational speed of the kick-down drum upon a speedchanging operation and can be calculated by multiplying a predeterminedgear ratio to a value of VSRPM2 similarly as described hereinabove. Alsohere at step S157, a current kick-down drum speed may be detected andused as a value of the rotational speed KDRPM3.

Subsequently at step S158, a throttle returning kick-down drum speedRTNRPM is determined from a one-dimensional map #MRTN34 shown in FIG.34(i) using the kick-down drum speed KDRPM3 as a parameter similarly asat step S111 of FIG. 31(i).

Then, at subsequent step S159, the speed change base torque SFTEM isplaced into the aimed engine output torque TOM, and then the sequenceadvances to step S117 of FIG. 31(i).

On the other hand, if it is judged at step S156 that the timer CSFTreaches the throttle closing timing TSHUT and consequently the sequenceadvances to step S160, it is judged at step S160 whether or not thecurrent kick-down drum speed KDRPM has decreased to a value smaller thanthe throttle returning kick-down drum speed RTNRPM.

After an up-shifting operation from the third to the fourth gearposition is started, the kick-down drum speed KDRPM begins to decreasein response to a closing movement of the throttle valve 31. However, ifthe value KDRPM is increased to or beyond the throttle returningkick-back drum speed RTNRPM at step S160, then the up-shifting shockreducing control of the present control cycle is completed, and thethrottle opening θ_(TH) is set to an opening instructed by way of theaccelerator or the like (an opening normally instructed). On the otherhand, if the kick-down drum speed KDRPM has not been increased to thethrottle returning kick-down drum speed RTNRPM at step S160, then it isdetermined that the increase of the kick-down drum speed KDRPM till thenis not yet sufficient, and the sequence advances to step S161 and thento step S162 at in order to set correction torque values T_(C1) andT_(C2) for the determination of temporary amounts of closing movement ofthe throttle valve 31 similarly as described hereinabove.

In short, at step S161, a correction torque T_(C1) is determined from aone-dimensional map #MTIM34 shown in FIG. 35 using a difference betweena time after starting of a closing movement of the throttle valve, (inshort, a the speed change timer CSFT) and the throttle closing timingTSHUT, that is, CSFT-TSHUT, as a parameter.

At subsequent step S162, another correction torque T_(C2) is determinedfrom another one-dimensional map #MRPM34 shown in FIG. 36 using thekick-down drum speed KDRPM3 before the closing movement of the throttlevalve as a parameter.

Further at step S163, a value obtained by subtraction of the correctiontorque values T_(C1) and T_(C2) from the speed change base torque SFTEM,that is, SFTEM-TC₂₁ -T_(C2) is placed into the aimed engine outputtorque TOM, and then the sequence advances to step S117 of FIG. 31(i).Then, an aimed throttle opening CPTG is determined at step S117, andthen at step S118, a maximum throttle opening THMAX is determined usingthe current engine speed DRPM as a parameter, similarly as describedhereinabove.

Then at subsequent step S119, it is judged whether or not the maximumthrottle opening THMAX is smaller than the aimed throttle opening CPTG,and if THMAX is not smaller than CPTG, the aimed throttle opening CPTGdetermined at step S117 is adopted, but on the contrary if THMAX issmaller than CPTG, the sequence advances to step S120 at which themaximum throttle opening THMAX is set to the aimed throttle openingCPTG, thereby completing the up-shifting shock reducing control of thepresent control cycle.

Since variations of the throttle valve 31, timer CSFT, kick-down drumspeed and torque of the output shaft of the torque converter 32 in shockreducing control upon up-shifting from the third to the fourth gearposition are substantially similar to those of the time charts uponup-shifting from the first to the second gear position shown in FIGS.32(i) to 32(iii), description thereof is omitted herein. As a result,also upon changing of the gear position from the third to the fourthgear position, the variation of the torque of the output shaft of theautomatic transmission 32, particularly rapid reduction of the torque ofthe output shaft of the automatic transmission 32 upon completion of aspeed changing operation, is moderated, and a speed change shock isreduced.

While the timing of starting of a closing movement of the throttle valve31 is determined with reference to the timer CSFT in the up-shiftingshock reducing control described above, a condition of rotation of thekick-down drum (K/D drum) may otherwise be detected so that the timingof starting of a closing movement of the throttle valve 31 may bedetermined in response to such rotation condition of the kick-down drum.

Advantages and effects of the system as an embodiment of the presentinvention which operates in such a manner as described above can besummarized in the following manner.

First, the following effects are obtained through the control of theengine 13 by the engine controlling system 1.

For an interval of time until the rotational speed of the engine 13rises to a rotational speed in a normal condition directly afterstarting of the engine 13, or when the operating condition of the engine13 becomes unstable due to some causes so that the rotational speed ofthe engine 13 is decreased, the throttle valve 31 operates in responseto movement of the accelerator pedal 27 in an equivalent condition tothat the accelerator pedal 27 and the throttle valve 31 are mechanicallycoupled directly to each other.

Accordingly, in this instance, control of the throttle valve executedthen does not depend upon a changing rate of the treadled amount of theaccelerator pedal nor upon a running condition of the vehicle or thelike. Accordingly, the throttle valve 31 is controlled stably, whichprevents the running condition of the engine 13 from being renderedunstable.

To the contrary, in case the brake pedal 28 is treadled so that brakingby the brake (not shown) of the vehicle is effected, the followingeffects can be attained.

Firstly, when such braking is being effected, since the throttle valve31 is normally held at the minimum opening corresponding to the engineidling position in priority to any other instruction of the automaticcruise switch 18, accelerator pedal 27 or the like, a braking effect byengine brake is attained in addition to braking by the brake (notshown).

Secondly, in case the duration of a condition wherein a deceleration isgreater than a reference value in braking by the brake continues for aninterval of time longer than a reference value and the speed of thevehicle upon cancelling of treadling of the brake pedal 28 is lower thana reference value, the throttle valve 31 is held at the minimum openingposition until the 10 accelerator pedal 27 is subsequently treadled.Accordingly, there is an effect that, in case the brake pedal 28 isreleased once directly after the vehicle has been stopped as a result ofdeceleration by the brake (not shown) in order to stop the vehicle at acrossing or the like, braking by engine brake is accomplished so thatthe vehicle is stopped smoothly and an impact upon stopping can beprevented.

Thirdly, in case, in braking by the brake, the deceleration does notexceed the reference value or such duration as described above is notlonger than the reference value or else the speed of the vehicle uponcancelling of such treadling as described above, the speed of thevehicle is maintained constant with an aimed speed defined by the speedof the vehicle at a point of time directly after cancelling of treadlingof the brake pedal 28 until the accelerator pedal 27 is subsequentlytreadled. Accordingly, there is no necessity of treadling theaccelerator pedal 27 in order to maintain the speed of the vehicle norof re-starting by manual operation for constant speed running controlwhich is cancelled each time the brake pedal 28 is treadled in aconventional constant speed running device. Accordingly, there is aneffect that the burden to a driver is moderated and constant speedrunning of the vehicle is facilitated on a road where traffic iscomparatively heavy.

Fourthly, upon transition to such a constant speed running condition asdescribed above, for an interval of time till a timing for opening orclosing movement of the throttle valve 31 which is encountered for thefirst time directly after cancelling of treadling of the brake pedal 28,the throttle valve 31 is temporarily opened or closed to a throttlevalve opening with which it is forecast for the vehicle to maintain theactual speed at a point of time directly after such cancelling.Accordingly, there is an effect that transition to a constant speedrunning condition of the vehicle can proceed rapidly and smoothly from apoint of time directly after cancelling of treadling of the brake pedal28.

Fifthly, where the throttle switch 47 provided on the automatic cruiseswitch 18 is positioned at the position [f], after the brake pedal 28 isreleased, the throttle valve 31 is normally maintained at the minimumopening corresponding to the engine idling position until theaccelerator pedal 27 is treadled subsequently. Accordingly, upon runningon a gentle descent or the like, the vehicle can run under additionalbraking by engine brake by changing over the throttle switch 47 to theposition [f].

Subsequently, there are following effects when the accelerator pedal 27is treadled.

Firstly, when the accelerator pedal 27 is treadled, an aimedacceleration DVS_(AC) designated by the automatic cruise switch 18 isadopted as an aimed speed of the vehicle until after an aimedacceleration DVS_(AP) based on such treadling of the accelerator pedal27 becomes greater than the aimed acceleration DVS_(AC) designated bythe automatic cruise switch 18. Accordingly, in case the acceleratorpedal 27 is treadled to change the control mode of the vehicle toaccelerator mode control while running of the vehicle is beingcontrolled in accordance with an aimed acceleration DVS_(AC) (duringautomatic cruise control), even if the treadling amount of theaccelerator pedal 27 is excessively small at an initial stage of suchchange, the aimed acceleration will not drop temporarily. Accordingly,there is an advantage that, when the accelerator pedal 27 is treadled toaccelerate the vehicle, the vehicle will be accelerated rapidly andsmoothly.

Secondly, an acceleration of the vehicle is set in accordance with atreadled amount of the accelerator pedal 27, a changing rate of thetreadled amount and an interval of time elapsed after the changing ratehas become lower than a reference value. Consequently, the more quicklythe accelerator pedal 27 is treadled, the more suddenly the vehicle isdecelerated, and thus the more moderately the accelerator pedal 27 istreadled, the more slowly the vehicle is decelerated. Accordingly,acceleration of the vehicle of a high responsibility upon which a willof the driver is reflected precisely can be attained. Also there is aneffect that the acceleration is changed smoothly if such treadling ismoderated or stopped and accordingly occurrence of an impact arisingfrom a sudden change in acceleration can be prevented.

Thirdly, after treadling of the accelerator pedal 27 is cancelled, thespeed of the vehicle is maintained constant with an aimed speed definedby the speed of the vehicle at a point of time directly after suchcancelling. Accordingly, there is no necessity of treadling theaccelerator pedal 27 again in order to maintain the speed of the vehicleconstant or of resetting an aimed speed each time the speed of thevehicle is changed by the accelerator pedal 27 as in a conventionalconstant speed running device. Accordingly, there are effects that theburden to the driver is moderated and that constant speed running on aroad where traffic is comparatively heavy is facilitated. The effectsbecome particularly remarkable by a combination with such constant speedrunning after cancelling of treading of the brake pedal 28 as describedabove.

Fourthly, upon transition to a constant speed running condition of thevehicle, for an interval of time till a timing for opening or closing ofthe throttle valve 31 which is encountered for the first time aftercancelling of treadling of the accelerator pedal 27, the throttle valve31 is temporarily opened or closed to a throttle valve opening withwhich it is forecast for the vehicle to maintain the actual speed at apoint of time directly after such cancelling. Consequently, there is aneffect that transition to a constant speed running condition from apoint of time directly after such cancelling can proceed rapidly andsmoothly.

Fifthly, when the shift selector 29 is at a position other than for theD range or when the throttle valve switch 47 is at the position [e], thethrottle valve 31 operates in response to movement of the acceleratorpedal 27 in an equivalent condition to that the accelerator pedal 27 andthe throttle valve 31 are mechanically coupled directly to each other.Accordingly, since the throttle 31 is moved in the closing direction iftreadling of the accelerator pedal 27 is moderated or stopped, thevehicle can run, upon running, for example, on a sloping road, underadditional braking by engine brake by moving the shift selector 29 tothe L range position or by changing over the throttle switch 47 to theposition [e].

Sixthly, among aimed accelerations which are set upon treadling of theaccelerator pedal, the aimed acceleration which is set in accordancewith the treadled amount of the accelerator pedal 27 exhibits, withrespect to a same treadled amount, a greater value during increase intreadled amount than during decrease in treadled amount as shown in FIG.20. Consequently, there is an effect that the acceleration of thevehicle is increased or decreased in response to transition fromincrease to decrease or from decrease to increase in treadled amount ofthe accelerator pedal 27 and the driving feeling is improved.

Further, when transition to a constant speed running condition is to beeffected in response to cancelling of treadling of the accelerator pedal27 or in response to cancelling of treadling of the brake pedal 27, theaimed acceleration is set so that the acceleration of the vehicle may begradually decreased finally to 0 as time passes after such cancelling oftreading. Accordingly, there is an effect that occurrence of an impactby a sudden change in acceleration upon transition to a constant speedrunning condition can be prevented.

Meanwhile, the following effects can be anticipated when the acceleratorpedal 27 and the brake pedal 28 are both in a released condition and thevehicle is in a constant speed running condition as describedhereinabove.

Firstly, one of three running conditions including accelerated running,decelerated running and constant speed running can be selected byoperation of the acceleration switch 45 or the changing over switch 46,and acceleration or deceleration to a final aimed speed or transition toconstant speed running after reaching of such final aimed speed isperformed automatically in response to a single operation of theacceleration switch 45 or the changing over switch 46. Accordingly,there is an effect that a change in speed of the vehicle in accordancewith situations during constant speed running on a highway or the likeis facilitated and the burden to the driver is moderated.

Secondly, in case the contact of the changing over switch 46 is changedto an on-state to designate accelerated running or decelerated running,the difference between a speed of the vehicle before such designationand a final aimed speed is increased if the duration of the on-state ofthe changing over switch 46 increases because an aimed speed VS is equalto a sum of an actual speed VA, a correction amount VK₁ and anothercorrection amount VT₁ corresponding to the duration of an on-state, thatis, VS=VA+VK₁ +VT₁, or a difference from an actual speed VA of acorrection amount VK₂ and another correction amount VT₂ corresponding tothe duration of an on-state, that is, VS=VA-VK₂ -VT₂. Therefore, when itis intended to effect acceleration or deceleration of the vehicle beyondthe final aimed speed, it is only necessary to change the contact of thechanging over switch 46 to an on-state again to redesignate acceleratedrunning or decelerated running and continue the on-state for a requiredperiod of time. Further, if the contact of the changing over switch 46is changed to an on-state while the vehicle is in an accelerated ordecelerated running condition, the vehicle is changed over to a constantspeed running condition wherein the speed of the vehicle at a point oftime directly after the contact of the changing over switch 46 has beenchanged to an on-state is employed as an aimed speed. Accordingly, incase a desired speed of the vehicle is reached before the final aimedspeed is reached, it is only necessary to operate the changing overswitch 46 once. In addition, since moderate acceleration, intermediateacceleration and quick acceleration are available for acceleratedrunning by means of the acceleration switch 45, the aforementionedeffects can be further promoted by combination of such operations.

Thirdly, if the speed of the vehicle changes suddenly on a sloping roador the like while the vehicle is in a constant speed running condition,then the aimed acceleration to restore the original speed of the vehicleis set to a value corresponding to a difference between an aimed speedand an actual speed detected by the speed detecting means and fallingwithin a range not greater than a predetermined value such that thedifference of the aimed acceleration from an acceleration of the vehicleat present may not exceed a preset value. Accordingly, there is aneffect that a quick change in acceleration is eliminated and occurrenceof an impact is prevented.

In case the acceleration switch 46 or the changing over switch 46 isoperated to designate such an accelerated running condition as describedhereinabove, the following effects can be anticipated.

Firstly, an aimed acceleration of a fixed value corresponding to theposition of the acceleration switch 45 is not designated immediatelyafter such designation of an accelerated running condition, but a slopeis provided for rising of the aimed acceleration (refer to FIG. 27), andthe aimed acceleration is designated such that the fixed value may beapproached and finally reached by the actual aimed acceleration of thevehicle. Accordingly, there is an effect that occurrence of an impact orhunting by a sudden change in acceleration when transition from aconstant speed running condition to an accelerated running conditiontakes place can be prevented.

Secondly, as the speed of the vehicle approaches a final aimed speed asa result of accelerated running, an aimed acceleration which decreasesas the speed of the vehicle approaches the final aimed speed isdesignated in place of an aimed acceleration of a fixed valuecorresponding to the position of the acceleration switch 45.Consequently, when the speed of the vehicle reaches the final aimedspeed, the acceleration of the vehicle changes smoothly and enters aconstant speed running condition. Accordingly, there is an effect thatoccurrence of an impact by a sudden change in acceleration can beprevented.

Thirdly, when the speed of the vehicle is lower than the referencevalue, an aimed acceleration having a value which increases as the speedrises and approaches an aimed acceleration of a fixed value set inaccordance with the position of the acceleration switch 45 is set againin place of the aimed acceleration of the fixed value. Accordingly,there is an effect that, if the acceleration switch 45 or the changingover switch 46 is operated to designate an accelerated running conditionduring slow running of the vehicle, acceleration of the vehicle iseffected more moderately and the driving feeling is improved.

To the contrary, in case the changing over switch 46 is operated todesignate a decelerated running condition as described hereinabove, whenthe speed of the vehicle approaches a final aimed speed as a result ofsuch decelerated running, an aimed deceleration which graduallyapproaches 0 as the speed of the vehicle approaches the final aimedspeed is designated in place of the aimed deceleration of a fixed valuetill then. Accordingly, there is an effect that, when the speed of thevehicle approaches a final aimed speed, the acceleration of the vehiclechanges smoothly and enters a constant speed running condition, andaccordingly, occurrence of an impact by a sudden change in accelerationis prevented and the driving feeding can be improved.

It is to be noted that, since, even if the aimed speed changing switch48 is operated, such instruction is ignored (steps J104 to J108 of FIG.16) during accelerated running or decelerated running other than duringconstant speed running, confusion in control is prevented and control ofthe engine is assured by the present system.

Further, if an operation is made to change the speed of the vehicleduring constant speed running, the vehicle will then make accelerated ordecelerated running. In this instance, however, an aimed acceleration isset in accordance with a difference VS-VA between a new aimed speed VSand an actual speed VA (refer to FIGS. 23 and 25), and the engine iscontrolled in accordance with the aimed acceleration to accomplishchanging of the speed of the vehicle. Accordingly, there is an effectthat occurrence of an impact by a sudden change in acceleration when thevehicle is changed over from a constant speed running condition to anaccelerated running condition in a similar manner as described above.

Particularly, since, when the difference VS-VA becomes smaller than afixed value (in short, the actual speed VA approaches the aimed speedVS), the aimed acceleration which has remained a fixed value so far isset such that it may decrease as the difference VS-VA decreases (referto the map #MDVS3 of FIG. 23 and the map #MDVS5 of FIG. 25), convergenceof the actual speed to the aimed speed is stabilized.

To the contrary, if the acceleration switch 45 or the changing overswitch 46 is operated to designate a constant speed running conditionwhile the vehicle is in an accelerated running condition or in adecelerated running condition, then the following effects can beanticipated.

Firstly, for an interval of time during transition to a constant speedrunning condition till a timing for opening or closing movement of thethrottle valve 31 which is encountered for the first time directly afteran operation for such transition, the throttle valve 31 is temporarilyopened or closed to a throttle valve opening with which it is forecastfor the vehicle to maintain the actual speed at a point of time directlyafter such operation. Accordingly, there is an effect that transition toa constant speed running condition directly after such operation canproceed rapidly and smoothly.

Secondly, since the aimed acceleration is gradually decreased (orincreased) for each throttle valve opening/closing cycle upon transitionto a constant speed running condition, the actual acceleration of thevehicle is gradually decreased (or increased) as time passes after theoperation by actuating the throttle valve 31 in accordance with thegradually decreasing (or increasing) aimed acceleration. Then, when theactual acceleration becomes smaller (or greater) than the referencevalue, the speed of the vehicle is employed as a new aimed speed VS, andthe aimed acceleration decreases (or increases) as the difference VS-VAdecreases (or increases) so that the vehicle finally enters a constantspeed running condition at a speed substantially equal to the aimedspeed VS. Accordingly, there is an effect that occurrence of an impactby a sudden change in acceleration upon transition to a constant speedrunning condition is prevented.

When the accelerator pedal 27 and the brake pedal 28 are both in areleased condition and automatic cruise mode control is being executed,the following effects can be attained.

Firstly, as a value of an actual acceleration which is used in automaticcruise mode control, one of DVA₆₅ which is high in follow-up performanceto an actual change in acceleration of the vehicle and is suitable forcontrol which requires a high responsibility, DVA₈₅₀ which is low ininfluence by an instantaneous disturbance and is suitable for controlwhich requires a high stability and DVA₁₃₀ which has intermediate valuesbetween the values of them is selectively used suitably upon starting ofa change in running condition, during the change in running condition orafter completion of the change in running condition.

Consequently, there is an effect that, when, for example, treadling ofthe accelerator pedal 27 is cancelled or treadling of the brake pedal 28is cancelled to place the vehicle into a constant speed runningcondition, and when the acceleration switch 45 or the changing overswitch 46 is operated to put the vehicle into a different runningcondition, starting of such transition can be effected rapidly andprecisely by using the value of DVA₆₅ in the control at a firstopening/closing timing for the throttle valve 31 after starting of suchtransition. Further, there is an effect that, by using DVA₈₅₀ after aconstant speed running condition is reached after such transition,stabilized control can be attained which is free from occurrence of anerror in operation by a disturbance.

Secondly, the timing at which the throttle valve 31 is to be opened orclosed is set with a cycle which increases in inverse proportion to achange in speed of the vehicle when the speed of the vehicle is varyingsuch that the vehicle is making accelerated or decelerated running as aresult of operation of any one of the running condition changing meanssuch as the accelerator pedal 27, brake pedal 28, acceleration switch 45and change-over switch 46. Accordingly, there is an effect that thefrequency of opening or closing movement of the throttle valve 31 perunit time increases as the speed of the vehicle rises and driving of thevehicle of a high responsibility can be attained.

Thirdly, by the first fail safe control wherein, in case an air pressuredetected by the air pressure detecting device of the air suspension ofthe car weight detecting section 19 (data corresponding to the weight ofthe vehicle) changes suddenly, data of an actual acceleration obtainedbefore such sudden change are adopted and control of the system isre-set to its initial condition, when it can be judged that an error hastaken place in an actual acceleration DVA found out by the thirdinterrupt control, latest ones of already calculated proper data (finalcalculated values) are adopted as data of the actual accelerations DVA(DVA₆₅, DVA₁₃₀ and DVA₈₅₀). Accordingly, even if a bump, a rebound orthe like of a wheel is caused, for example, by an uneven configurationof a road surface to cause an error in car speed data, no erredacceleration data will be adopted. Consequently, there are advantagesthat running control of the vehicle is made smooth without beinginfluenced by a disturbance, that desired control can be executedrapidly because possible latest acceleration data are adopted, and thata driving or operating feeling can be improved.

Further, by the second fail safe control which is executed in a parallelrelationship to the first fail safe control, an error in actualacceleration data can be discriminated in accordance with anacceleration in a car body advancing direction detected by the G sensor51. Consequently, even an error in actual acceleration data which doesnot arise from a bump, a rebound or the like of a wheel can be detectedwith certainty. Accordingly, an influence of a disturbance on runningcontrol of the vehicle can be eliminated in a wider range than in thefirst fail safe control, and the second fail safe control can contributeto improvements in driving feeling and so forth executing desiredcontrol smoothly and rapidly while using latest acceleration data as faras possible similarly as in the first fail safe control.

It is to be noted that only one of the first and second fail safecontrols in which errors in actual acceleration data are detected andprocessed may otherwise be executed.

Then, after a constant speed running condition is entered, since thespeed of the vehicle is substantially constant and no great variation inopening of the throttle valve is involved, the timing described above isset with a constant period independent of the speed of the vehicle.Consequently, there is an effect that, even if the rate of high speedrunning is increased, possible deterioration in life of the throttlevalve 31 and the throttle valve pivoting section 26 is prevented.

Further, while every control is executed for a constant control period(control cycle) mainly in accordance with the main flow chart shown inFIG. 8(i), since the control period is set to a time (Ta+Td) obtained byan addition of a predetermined time Ta to a time (loss time) Td whichcorresponds to a delay of control which may be caused by inertia of thetorque converter, the transmission and so forth of the vehicle, apossible response delay to control will not have an influence on a nextcontrol cycle. Accordingly, accurate control can always be realized,which is advantageous in realization of a desired running condition.

Then, aimed torques in engine control such as an aimed torquecorresponding to operation of the accelerator pedal (refer to theexpression (2) above) and an aimed torque upon constant speed running(refer to the expression (1) above) are found out as values at the firstgear position by converting them into such values which are applicablewhen the first gear position of the automatic transmission 32 is used.Since the torque values at the first gear position present higher valuesthan those at any other gear position, there is an advantage that, whenan aimed throttle opening is calculated from an aimed torque and anengine rotational speed, the resolution is high and the relative erroris low.

On the other hand, where an actual torque from which aimed torques TOM₁,TOM₂ and TOM₃ (refer to the expressions (1), (5) and (4) above) are tobe calculated is found out otherwise using, for example, an intake airamount as a parameter, a comparatively great delay occurs in controlbecause a detection value of an intake air is delayed with respect tooperation of the throttle valve. With the present system, however, sincean actual torque TEM is found out in accordance with characteristics ofthe automatic transmission (torque converter) 32, there is an advantagethat such possible control delay is prevented and and a highresponsibility in control is assured.

Further, there is an advantage that, since not a fixed value but apossible latest measured value is employed as data of the weight W ofthe vehicle which is important for the control of the engine, even whena passenger or passengers or a load changes, the engine can becontrolled appropriately with a high degree of accuracy taking suchchange into consideration rapidly.

Then, in case the throttle actuator 40 of the throttle valve pivotingsection 26 fails, when the gear position of the automatic transmissionthen is in the P range or the N range, the engine speed is lowered to apredetermined level (for example, to an idling speed level or so) and arise of the engine speed is restricted, and accordingly, rapid stoppingof the vehicle can be achieved. On the other hand, when the gearposition of the automatic transmission is in the D range or some otherrange, the speed of the vehicle can be adjusted within a fixed range(within which a rise of the engine speed can be restricted) in responseto the accelerator pedal position APS. Accordingly, there is anadvantage that, even after the throttle valve pivoting section 26 fails,it is possible to drive the vehicle, for example, to a suitablelocation.

While various advantages and effects of the control of the engine 13 bythe engine controlling system 1 are described so far, advantages andeffects of the control of the automatic transmission 32 by the automatictransmission controlling means 107 of the engine controlling system 1are described below.

When automatic cruise mode control is being executed without treadlingthe accelerator pedal 16, gear position control of the automatictransmission 32 is executed setting a pseudo treadled amount SFTAPS.Accordingly, gear position control in automatic cruise mode control canbe executed in a substantially common technique to that in gear positioncontrol in accelerator mode control, and there is an advantage that gearposition control can be executed readily and with certainty even whenautomatic cruise mode control is being executed. Particularly because apseudo treadled amount SFTAPS upon accelerated running is set in advancein a map as a value corresponding to a set aimed acceleration DVS,reliable control of a high responsibility can be achieved.

When the vehicle is to ride on a steep upward or downward slope, it issometimes difficult for the vehicle to maintain constant speed runningin automatic cruise mode control only by such control of the engine 13.In such an instance, the gear position of the automatic transmission 32is suitably shifted down by operation of the automatic transmissioncontrolling means 107. Consequently, there is an advantage that thetorque of the engine is increased upon riding on an upward slope but theengine brake is rendered more effective upon riding on a downward slopeso that constant speed running can be maintained with certainty.

Particularly, the control by the automatic transmission controllingmeans 107 necessitates, when a down-shift is to be carried out, thesatisfaction of all of the requirements: (1) the actual speed of thevehicle is excessively low; (2) a condition wherein the actualacceleration is lower than a predetermined value continues for apredetermined period of time; (3) the current gear position is eitherthe third or the fourth gear position; (4) a condition wherein asubstantially maximum torque is produced at a current engine rotationalspeed continues for a predetermined period of time; and (5) an enginerotational speed after carrying out of a down-shift does not exceed apredetermined value. Accordingly, a down-shift is not carried outinadvertently within a range within which the speed of the vehicle canbe maintained by the control of the engine 13, and the rotational speedof the engine 13 will not be increased excessively as a result of adown-shift.

Then, upon such down-shift, an up-shift is inhibited simultaneously, andcancellation of such inhibition of an up-shift requires the satisfactionof all of the requirements: (1) an up-shift is inhibited; (2) the actualspeed of the vehicle is approaching an aimed speed; (3) the current gearposition is either the second or the third gear position; and (4) acondition wherein the output torque of the engine is sufficiently highat present continues for a predetermined period of time. Consequently,an up-shift is enabled only when a condition wherein the speed of thevehicle can be maintained only by the control of the engine 13 isentered after carrying out of the up-shift. Accordingly, an unnecessarygear change is prevented, and the maintenance of constant speed runningis further assured.

Further, in case quick braking is performed by way of the brake pedal16, when the gear position of the automatic transmission 32 is set to ahigh speed gear position, a shifting down operation is performed at anearlier stage in proportion to a degree of such quick braking, andaccordingly, the effect of engine brake is increased. Thus, brakingforce by such engine brake is added to braking force derived from thebrake pedal 16, and accordingly, the braking faculty is improved verymuch.

Upon such speed changing operation of the automatic transmission 32, aspeed change shock may possibly be caused by a variation of torque ofthe output shaft of the automatic transmission 32 such as a suddendecrease at a time of completion of the speed changing operation. Thus,there is an effect that a shock which likely takes place upon a speedchanging operation is moderated and a driving feeling is improvedbecause the throttle opening of the engine 13 is temporarily decreased(closed) for a period of time after starting till completion of an upshifting operation to restrict a variation of torque of the output shaftof the automatic transmission 32. Particularly in the case of thepresent embodiment, since the throttle opening θ_(TH) is preliminarilydecreased a little before it is decreased formally, the controllingspeed can be increased without making an obstacle to stabilized controlof torque, and the controlling capability of reducing a speed changeshock is improved.

Further, since, in speed change shock reducing control of the presentsystem, a rotating condition of the kick-down drum is detected andstarting of a closing movement of the throttle opening of the engine 13is determined directly in accordance with the thus detected rotatingcondition of the kick-down drum, the throttle opening can be controlledwith certainty in response to an operating condition of the automatictransmission 32. Accordingly, moderation of a gear change shock can beperformed with a higher degree of accuracy and a shock upon a speedchanging operation can be moderated very appropriately.

It is to be noted that, while in the embodiment described above theaimed acceleration DVS is caused to gradually approach zero as means forcausing the speed of the vehicle to approach an aimed speed VS upontransition to a constant speed running condition by automatic cruisemode control, such means may otherwise include a first aimed speed VS₁(which substantially corresponds to the aimed speed VS in theembodiment) and a second aimed speed VS₂ as described below.

For example, in case the accelerator pedal 27 is treadled to acceleratethe vehicle and then the treadling of the accelerator pedal 27 iscancelled, at first the actual speed VA_(I) immediately after suchcancellation is set as a first aimed speed VS₁, and then the throttlevalve 31 is temporarily pivoted to an opening position at which it isestimated that the speed of the vehicle may maintain the first aimedspeed VS₁.

Then, when a first throttle valve opening/closing timing cycle isentered in any following control cycle, the opening of the throttlevalve 31 is adjusted to control the engine 13 so that the actual speedVA may approach a second aimed speed VS₂ while the second aimed speedVS₂ is changed so as to gradually approach the first aimed speed VS₁.

Finally, the speed of the vehicle is maintained in a fixed conditionwherein it substantially coincides with the first aimed speed VS₁.

Where the speed of the vehicle approaches the aimed speed VS in thismanner, there is an effect that the speed of the vehicle in a constantspeed running condition coincides further accurately with a speed of thevehicle immediately after cancellation of treadling of the acceleratorpedal 27.

Or else, not the first aimed speed VS₁ but the second aimed speed VS₂may be adopted as an aimed speed for constant speed running in a firstthrottle valve opening/closing timing cycle after cancellation oftreadling of the accelerator pedal 27 in order to minimize thedifference between an aimed speed and an actual speed of the vehicleimmediately before the throttle valve 31 is opened or closed in thefirst throttle valve opening/closing timing cycle. This will eliminate asudden change in speed and acceleration of the vehicle when the throttlevalve 31 is opened or closed in a throttle valve opening/closing cycle.Consequently, there is an effect that occurrence of a disagreeable shockis prevented and a very smooth change in speed can be realized.

Similarly, a first aimed speed VS₁ and a second aimed speed VS₂ may beset to open or close the throttle valve 31 when the brake pedal 28 istreadled to decelerate the vehicle and then the treadling of the brakepedal 28 is cancelled except a case wherein a condition wherein thedeceleration is higher than a reference value continues for a period oftime longer than a reference period of time and the speed of the vehicleupon cancellation of treadling of the brake pedal 28 is lower than areference value. Consequently, there is an effect that the speed of thevehicle in a constant speed running condition coincides furtheraccurately with a speed of the vehicle immediately after cancellation oftreadling of the brake pedal 28.

Further, if the second aimed speed VS₁ is adopted as an aimed speed forconstant speed running immediately in a first throttle valveopening/closing timing cycle after cancellation of treadling of thebrake pedal 28, then the difference between an aimed speed and an actualspeed of the vehicle immediately before opening or closing of thethrottle valve 31 in the first throttle valve opening/closing timingcycle is reduced. This will eliminate a sudden change in speed andacceleration of the vehicle when the throttle valve 31 is opened orclosed in the throttle valve opening/closing timing cycle. Accordingly,there is an effect that a disagreeable shock does not occur and a verysmooth speed change can be realized.

It is to be noted that such a throttle valve opening/closing timingcycle as mentioned above corresponds to an engine output adjustingperiod.

In the meantime, the engine controlling system 1 can be installed notonly in a vehicle which has such an automatic transmission 32 asdescribed above but also in a vehicle which has a manual transmission.In the following, description is given of an arrangement wherein theengine controlling system 1 is installed in a vehicle having a manualtransmission.

In this instance, the construction of the engine controlling system 1shown in FIG. 2 should be modified in the following regards.

In short, the output rotational speed detecting section 22 is eliminatedand a manual transmission (not shown) is provided in place of theautomatic transmission 32, and a shift lever (not shown) for manuallyselecting a gear position of the manual transmission is provided inplace of the shift selector 29. Further, the shift selector 17 isreplaced by a shift position switch (not shown) which has a contactwhich presents an on-state when the shift lever is positioned at aneutral position or at a position for rearward running or when a clutchpedal (not shown) is treadled.

Contents of control executed by the engine controlling system 1 which ismodified for the manual transmission in such a manner as described justabove are modified in the following points to those of the first andsecond embodiments.

In short, in the control executed at step A113 of FIG. 8(i), it isjudged whether or not the contact of the shift position switch (notshown) is in an on-state. Then, if it is judged that the contact is inan on-state, then the sequence advances to step A117, but on thecontrary if it is judged that the contact is in an off-state, then thesequence advances to step A114.

Meanwhile, the value of the speed ratio e for calculating a torque ratioT_(Q) in the equation (1) used at step C130 of FIG. 10, the equation (2)used at step D123 of FIG. 11, the equation (4) used at step E107 of FIG.12 and the equation (5) used at step E123 of FIG. 12 is equal to 1.

Operation of the engine controlling system 1 having such a constructionas described above is different from that of the engine controllingsystem 1 of the first and second embodiments only at step A113 which ismodified as described above.

In particular, when the shift lever is at the neutral position or at theposition for rearward running or when the clutch pedal (not shown) istreadled, the contact of the shift position switch is in an on-state.Accordingly, depending upon such judgment at step A113, the sequenceadvances to step A117 at which direct throttle movement is performed ina similar manner as in the embodiment.

To the contrary, when the shift lever is positioned at any otherposition than the neutral position and the position for rearward runningand the clutch pedal is not treadled, the contact of the shift positionswitch is in an off-state. Accordingly, depending upon such judgment atstep A113, the sequence advances to step A114 at which control isexecuted in a similar manner as in the embodiment.

Accordingly, also where such engine controlling system 1 is installed ina vehicle which has a manual transmission, substantially similar effectsto those of an alternative arrangement wherein the engine controllingsystem 1 is installed in a vehicle which has such automatic transmission32 can be attained.

Meanwhile, the shift lever of such an engine controlling system asdescribed above may have, at a position thereof at which the shiftposition switch presents an on-state, a first speed position which maybe used as the low gear position, or such a first speed position and asecond speed position as the second gear position, or otherwise suchfirst and speed positions and a third speed position as the third gearposition.

Description of the engine controlling system 1 as installed in thevehicle which has the manual transmission is thus completed.

The engine controlling system of the embodiment described hereinabovemay have such modification as described below.

When the acceleration switch 45 or the changing over switch 46 isoperated to designate an accelerated running condition or a deceleratedrunning condition while automatic cruise mode control is executed in acontrol cycle and the vehicle is in a constant speed running condition,a set value of a final aimed speed may be modified by the final aimedspeed setting section 6 of the control section 25.

In short, the set value of the final aimed speed then is a sum of acorrection amount VK₁ and an actual speed VA detected by thespeed/acceleration detecting section 24 when an accelerated runningcondition is designated but is a difference of a correction amount VK₂from an actual speed VA detected by the speed/acceleration detectingsection 24 when a decelerated running condition is designated. However,the final aimed speed may be set otherwise by multiplying an actualspeed VA by a present coefficient.

Or else, an aimed speed VS while the vehicle has been in a constantspeed running condition may be employed in place of an actual speed VA.Meanwhile, substantially similar effects can be attained if the twocorrection amounts VK₁ and VK₂ have a same value.

Subsequently, when the changing over switch 46 is operated to designatea decelerated running condition while the vehicle is in a constant speedrunning condition, the aimed acceleration may be increased gradually foreach control cycle after such designation similarly as when anaccelerated running condition is designated. In this instance, inaddition to the effects attained by the embodiments describedhereinabove, there is an effect that transition to decelerated runningproceeds further smoothly.

To the contrary, in case the throttle switch 47 is moved to the position[f], the throttle valve 31 is normally maintained at its minimum openingposition corresponding to the engine idling position after cancelling oftreadling of the brake pedal 28. In this instance, the throttle valve 31may be normally maintained at its minimum opening position further aftercancelling of treadling of the accelerator pedal 27.

Further, the acceleration switch 45 has the four positions [a] to [d]shown in FIG. 6, and in case changing over of the acceleration switch 45is effected without effecting operation of the changing over switch 46,if the acceleration switch 45 is changed over to the position [a],constant speed running is designated, but if the acceleration switch 45is changed over to any of the positions [b] to [d], accelerated runningis designated by the running condition designating section 3 of thecontrol section 25. However, running conditions corresponding to thepositions [a] to [d] may not be limited to such as described above, andarbitrary running conditions may be designated by the individualpositions [a] to [d] of the acceleration switch 45.

Further, while decelerated running is not designated by mere changingover of the acceleration switch 45 in the embodiments described above,one of the four positions of the acceleration switch 45 may be aposition for selective setting of decelerated running in order to enabledesignation of deceleration running by mere changing over of theacceleration switch. Besides, selection of the acceleration switch 45 isnot limited to the four positions [a] to [d] and may otherwise have anincreased or decreased number of positions.

In addition, changing over of a running condition corresponding tooperation of the changing over switch 46 is not limited to such asdescribed hereinabove in connection with the embodiments, and arbitraryrunning conditions may be set in combination for each position of theacceleration switch 45 so that they may be changed over in response tooperation of the changing over switch 46.

Subsequently, in case, when deceleration of the vehicle is performed bythe brake (not shown), the duration of a condition wherein decelerationof the vehicle is greater than a reference value is longer than areference interval of time and the speed of the vehicle upondeceleration is lower than a reference value, the throttle valve 31 ismaintained at the minimum opening corresponding to the engine idlingposition continuously after cancelling of releasing of the brake pedal28. The requirements may be modified in accordance with characteristicsor an object for use of the vehicle.

The requirement for holding the throttle valve to the engine idlingposition may be such, for example, as follows.

In particular, a requirement may be (1) that the deceleration upontreadling of the brake pedal is greater than the reference value, or (2)that the duration of a treadled condition of the brake pedal is longerthan the reference value, or else (3) that the speed of the vehicle uponcancelling of treadling of the brake pedal is lower than the referencevalue. Or, as a requirement provided by a suitable combination of therequirements listed above, a requirement may be, for example, (4) thatthe deceleration upon treadling of the brake pedal is greater than thereference value and the speed of the vehicle upon deceleration (speed ofthe vehicle upon cancelling of treadling of the brake pedal) is lowerthan the reference value, or (5) that the duration of a conditionwherein the deceleration upon treadling of the brake pedal is greaterthan the reference value is longer than the reference value.

Meanwhile, although judgment of a degree of deceleration is madedepending on deceleration, it may otherwise be made depending on amagnitude of pressure of brake oil for actuating the brake.

Further, automatic cruise mode control is executed in each controlcycle. An additional function may be provided of indicating an aimedspeed for constant speed running when constant speed running isdesignated as a running condition of the vehicle but indicating a finalaimed speed for accelerated running or for deceleration running whenaccelerated running or decelerated running is designated. In thisinstance, changing of a set value of an aimed speed or a final aimedspeed can be made while confirming the same by eyesight.

Further, in the engine controlling system 1 of the embodiments describedabove, when the accelerator pedal 27 and the brake pedal 28 are both ina released condition, constant speed running is normally designated as arunning condition of the vehicle except a special case. However,constant speed running may otherwise be performed only when constantspeed running is designated artificially as in a conventional system. Inthis instance, since designation of a running condition is madeartificially, similar effects can be attained by rendering the enginecontrolling system 1 operative when the vehicle is accomplishingconstant speed running.

In addition, in the engine controlling system of any of the embodiments,without designating constant speed running as a running condition of thevehicle when merely the accelerator pedal 27 and the brake pedal 28 areboth put into a released condition, constant speed running may bedesignated when the acceleration switch 45 or the changing over switch46 is changed to effect changing over to a preset condition, that is,when the acceleration switch 45 in the embodiments is changed over tothe position [a].

Furthermore, the constants k₁ to k₁₀, the set rotational speeds XDRPM1to XDRPM6 and so forth which are used in the down-shift control (referto FIGS. 28(i) to 28(iii)) of the automatic transmission 32 executed bythe automatic transmission controlling device are not limited to thespecific set values used in the embodiment described above and may beset to suitable values in accordance with characteristics of an engineand/or a transmission.

INDUSTRIAL APPLICABILITY OF THE INVENTION

As described hereinabove, an engine controlling system of the presentinvention is useful as a controlling system for an engine of a vehicleof the type wherein the opening of a throttle valve of the engine iscontrolled by means of an electrically driven throttle actuator.Particularly where the engine controlling system of the presentinvention is applied to a controlling system for an engine of anautomobile which employs an electrically driven throttle actuator inorder to automatically control running of the automobile, thereliability of the controlling system can be improved significantly.

What is claimed is:
 1. An engine controlling system for a vehicle,comprising:an accelerator pedal of said vehicle, an operation amountdetecting means for detecting an operation amount of said acceleratorpedal and developing a corresponding operation amount detection signal,a throttle valve for changing an amount of air to be taken into anengine of said vehicle to adjust an output power of said engine, athrottle valve control amount setting means for setting a control amountof said throttle valve in response to the operation amount detectionsignal, a throttle valve controlling means for controlling said throttlevalve to open or close in response to the control amount, an abnormalcondition detecting means for detecting an abnormal condition of atleast one of said throttle valve controlling means and said throttlevalve control amount setting means and developing a correspondingabnormal condition detection signal, a speed change gear means providedin said vehicle and having a plurality of gear positions, an automaticspeed change gear controlling means for controlling changing overbetween the gear positions of said speed change gear means, a rangechanging over means for selectively setting a range of said speed changegear means at least to a running range or neutral range, a rangedetecting means for detecting a range set by said range changing overmeans and developing a corresponding range detection signal, an enginespeed detecting means for detecting a rotational speed of said engineand developing a corresponding engine speed detection signal, an engineoutput reducing means for reducing the output power of said engineindependently of said throttle valve, and an output reduction controlamount setting means for setting, when the abnormal condition detectionsignal is developed and the range detection signal indicates the neutralrange, a control amount of said engine output reducing means such that areduction of the output power of said engine is increased as the enginespeed represented by the engine speed detection signal increases, butsetting, when the abnormal condition detection signal is developed andthe range detection signal indicates the running range, a control amountof said engine output reducing means such that the reduction of theoutput power of said engine is decreased as the accelerator pedaloperation amount represented by the operation amount detection signalincreases.
 2. An engine controlling system for a vehicle as claimed inclaim 1, wherein said abnormal condition detecting means includes: acontrol amount detecting section for detecting an actual control amountof said throttle valve and developing a corresponding control amountdetection signal, and an abnormal condition detection signal developingsection for developing an abnormal condition detection signal when thedifference between an actual control amount of said throttle valverepresented by the control amount detection signal and a control amountset by said throttle valve control amount setting means comes out of apredetermined range.
 3. An engine controlling system for a vehicle asclaimed in claim 2, wherein said abnormal condition detection signaldeveloping section is set so as to develop an abnormal conditiondetection signal when the condition wherein the difference between anactual control amount of said throttle valve represented by the controlamount detection signal and a control amount set by said throttle valvecontrol amount setting means is outside the predetermined rangecontinues for a predetermined period of time.
 4. An engine controllingsystem for a vehicle as claimed in claim 2, wherein said engineincludes:a bypass passage which bypasses said throttle valve, and abypass passage opening/closing section interposed in said bypass passagefor opening and closing movement to adjust the amount of air to flowthrough said bypass passage, and wherein said output reduction controlamount setting means includes:an air amount judging section forcomparing, when the abnormal condition detection signal is developed, anactual control amount of said throttle valve with a control amount setby said throttle valve control amount setting means, and developing,when the actual control amount is smaller than the set control amount byan amount greater than a predetermined value, an air amount shortagesignal, but developing, when the actual control amount is greater thanthe set control amount by an amount greater than the predeterminedvalue, an air amount surplus signal, and an opening/closing controllingsection for opening or closing said bypass passage opening/closingsection in response to an output of said air amount judging section. 5.An engine controlling system for a vehicle as claimed in claim 1,wherein said engine output reducing means reduces the ratio of an amountof fuel to an amount of air of fuel air mixture to be supplied to saidengine to reduce the output power of said engine.
 6. An enginecontrolling system for a vehicle as claimed in claim 1, wherein saidengine output reducing means delays the phase angle of the ignitiontiming of said engine reduce the output power of said engine.
 7. Anengine controlling system for a vehicle as claimed in claim 1, whereinsaid engine output reducing means interrupts fuel to be supplied to allor part of cylinders of said engine to reduce the output power of saidengine.
 8. An engine controlling system for a vehicle as claimed inclaim 1, wherein said range changing over means is capable of changingover the range of said speed change gear means, when the range is to bechanged over to a forward running range.
 9. An engine controlling systemfor a vehicle as claimed in claim 1, wherein said range changing overmeans is changes over the range of said speed change gear means, whenthe range is to be changed over to a backward running range.
 10. Anengine controlling system for a vehicle, comprising:an accelerator pedalof said vehicle, an operation amount detecting means for detecting anoperation amount of said accelerator pedal and developing acorresponding operation amount detection signal, a throttle valve forchanging an amount of air to be taken into an engine of said vehicle toadjust an output power of said engine, a throttle valve control amountsetting means for setting a control amount of said throttle valve inresponse to the operation amount detection signal, a throttle valvecontrolling means for controlling said throttle valve to open or closein response to the control amount, an abnormal condition detecting meansfor detecting an abnormal condition of at least one of said throttlevalve controlling means and said throttle valve control amount settingmeans and developing a corresponding abnormal condition detectionsignal, a speed change gear means provided in said vehicle and having aplurality of gear positions, an automatic speed change gear controllingmeans for controlling changing over between the gear positions of saidspeed change gear means, a range changing over means for selectivelysetting a range of said speed change gear means at least to a runningrange or neutral range, a range detecting means for detecting a rangeset by said range changing over means and developing a correspondingrange detection signal, an engine speed detecting means for detecting arotational speed of said engine and developing a corresponding enginespeed detection signal, an engine output reducing means for reducing theoutput power of said engine, and an output reduction control amountsetting means for setting, when the abnormal condition detection signalis developed and the range detection signal indicates the neutral range,a control amount of said engine output reducing means such that areduction of the output power of said engine is increased as the enginespeed represented by the engine speed detection signal increases, butsetting, when the abnormal condition detection signal is developed andthe range detection signal indicates the running range, a control amountof said engine output reducing means such that the reduction of theoutput power of said engine is decreased as the accelerator pedaloperation amount represented by the operation amount detection signalincreases, wherein said throttle valve control amount setting meansincludes: an accelerator pedal operation condition detecting section fordeveloping a treadled condition detection signal when it detects atreadled condition of said accelerator pedal but developing a treadledcondition cancellation detection signal when it detects cancellation ofa treadled condition of said accelerator pedal, a first control amountsetting section for setting, when the treadled condition detectionsignal is developed, a control amount of said throttle valve in responseto the operation amount detection signal, a running condition selectingsection for selectively outputting, when the treadled conditioncancellation detection signal is developed, either one of a constantspeed running designating signal which designates constant speed runningas an aimed running condition of said vehicle and an accelerated runningdesignating signal which designates accelerated running as an aimedrunning condition of said vehicle, an aimed speed setting section forsetting, when the constant speed running designating signal isdeveloped, an aimed speed of said vehicle for the constant speedrunning, a running speed of said vehicle and developing a correspondingrunning speed detection signal, a second control amount setting sectionfor setting, when the constant speed running designating signal isdeveloped, a control amount of said throttle valve with which therunning speed of said vehicle represented by the running speed detectionsignal is to be made equal to the aimed speed, an accelerated runningaimed acceleration setting section for setting, when the acceleratedrunning designating signal is developed, an aimed acceleration for theaccelerated running of said vehicle, and a third control amount settingsection for setting, when the accelerated running designating signal isdeveloped, a control amount of said throttle valve in response to theaimed acceleration set by said accelerated gunning aimed accelerationsetting section.
 11. An engine controlling system for a vehicle asclaimed in claim 10 wherein said running condition selecting sectionincludes: a manual selecting section for selecting either one ofconstant speed running and accelerated running as an aimed runningcondition of said vehicle by manual operation thereof, a designatingsignal developing section for developing, when constant speed running isselected by said manual selecting section, a constant speed runningdesignating signal, but developing, when accelerated running is selectedby said manual selecting section, an accelerated running designatingsignal, a final aimed speed setting section for setting, when theaccelerated running designating signal is developed, a final aimed speedfor the accelerated running of said vehicle, and a running conditionchanging over section for changing over, when the absolute value of adeviation between a running speed of said vehicle represented by therunning speed detection signal and the final aimed speed of said vehiclebecomes smaller than a predetermined value, the output of saiddesignating signal developing section from an accelerated runningdesignating signal to a constant speed running designating signal. 12.An engine controlling system for a vehicle as claimed in claim 10wherein said first control amount setting section includes: a treadledcondition aimed acceleration setting section for setting, when thetreadled condition detection signal is developed, an aimed accelerationof said vehicle in response to the accelerator pedal operation amountrepresented by the operation amount detection signal and a changing rateof the accelerator pedal operation amount, a treadled condition aimedoutput calculating section for calculating an aimed output power of saidengine in response to the aimed acceleration set by said treadledcondition aimed acceleration setting section, and a treadled conditioncontrol amount calculating section for calculating a control amount ofsaid throttle valve in response to the aimed engine output powercalculated by said treadled condition aimed output calculating section.13. An engine controlling system for a vehicle as claimed in claim 10wherein said second control amount setting section includes: a constantspeed running aimed acceleration calculating section for calculating,when the constant speed running designating signal is developed, anaimed acceleration of said vehicle with which the running speed of saidvehicle represented by the running speed detection signal is to be madeequal to the aimed speed of said vehicle, a constant speed running aimedoutput calculating section for calculating an aimed output power of saidengine in response to the aimed acceleration calculated by said constantspeed running aimed acceleration calculating section, and a constantspeed running control amount calculating section for calculating acontrol amount of said throttle valve in response to the aimed engineoutput power calculated by said constant speed running aimed outputcalculating section.
 14. An engine controlling system for a vehicle asclaimed in claim 10 wherein said accelerated running aimed accelerationsetting section is capable of setting an aimed acceleration having anegative value.
 15. An engine controlling system for a vehicle asclaimed in claim 10 wherein said third control amount setting meansincludes: an accelerated running aimed output calculating section forcalculating, when the accelerated running designating signal isdeveloped, an aimed output power of said engine in response to the aimedacceleration set by said accelerated running aimed acceleration settingsection, and an accelerated running control amount calculating sectionfor calculating a control amount of said throttle valve in response tothe aimed engine output power calculated by said accelerated runningaimed output calculating section.